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.com Good evening everyone out there in radio
land. It's HamTalk Live episode number 99. Receiver
data on the ICOM 7610 and receiver comparisons
with Rob Sherwood NC0B recorded almost live on
Thursday January 25th 2018. I'm your host Neil
Rapp WB9VPG. Thanks for tuning in to this episode
of HamTalk Live. Tonight we're joined by Rob
Sherwood in C0B from Sherwood Engineering and
last week on the show Jerry Buxton in Zero JY
was here to talk about building satellites and
AMSAT's new Fox 1D. If you missed the show, you
can listen anytime. Just go to HamTalkLive .com
and you can listen to us there, or you can listen
to the podcast version. It's on just about every
podcast app out there. Upload to Apple Podcasts,
Stitcher, iHeart Podcasts, Google Play, TuneIn,
and SoundCloud. We're also over on YouTube, so
you can pick us up anywhere there. Well, normally
we try to have a live call -in segment with our
guests, but due to some scheduling conflicts,
Rob Sherwood wasn't able to be with us live tonight.
So as they say on The Gong Show, tonight we're
almost live! But he did record an interview and
so we took questions by social media in advance
of the show. So we are going to answer some listener
questions tonight, but we won't be doing that
live. So tonight I'll be playing the interview
and then afterwards I'll follow up with reading
his answers to the questions that came in. ahead
of time. So we'll do that and I'll be back with
Rob right after this word from Tower Electronics
right here on HamTalk Live. This episode of HamTalk
Live is brought to you in part by Tower Electronics.
Tower Electronics has been the Ham's Dime Store
since 1978. When you need connectors, mobile
and handheld antennas, cables, or adapters, visit
Scott or Jill at a HamFest near you. Or you can
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-2973. Stock up on those supplies like PL -259
and end connectors, SMA adapters, audio cables,
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house is a sign of a broken radio. You're listening
to HamTalk Live with Neil Rapp. Thanks as always
to Scott and Jill at Tower Electronics for helping
bring you HamTalk Live tonight. This weekend
they're at Arcadia, Florida at the ham fest there
on Saturday and also Saturday Jill will be over
in Collinsville, Illinois and Then February 9th
10th and 11 they'll be at hamcation in Orlando,
Florida So if you're at any of those shows, make
sure you look for tower electronics And if you're
not, you can give them a call at 920 -435 -2973
or visit their website at PL -259 .com and tell
them you heard it on HamTalk Live. Well, tonight's
guest is Rob Sherwood, NC0B. He first licensed
in 1961 with a novice license, WN8ADB, at age
14 in Cincinnati, Ohio. He upgraded to General
Class in about two months and changed his call
sign to WA8ADB. He operated as Portable Zero
in the mid -70s out of Colorado, and now he lives
there just east of Fort Collins. He upgraded
to Advanced and Extra in the 80s and that's when
he got his current call sign NC0B. In 1974 Rob
founded Sherwood Engineering offering Drake radio
upgrades which he still does today. He started
testing transceivers in 1976, and that total
has grown now over 100. And that data is available
online at his website, Sherwood Engineering.
And that's S -H -E -R -W -E -N -G dot com. NC0B
dot com will get you there as well. Sherwood
Engineering now offers modifications to many
shortwave receivers. and is an authorized dealer
of Japan radio receivers and still makes parts
and upgrades for the Drake R4C including roofing
filters, crystals, capacitor replacement kits,
and even owner's manuals. So as they say on the
sports cast, let's go to the tape. All right,
tonight we're with Rob Sherwood of Sherwood Engineering,
NC0B and He's had a chance to do some testing
on the ICOM 7610 and do some of his receiver
performance comparisons, and we've had him on
the show before. In fact, I think, Rob, you're
still the top -rated show on the program. All
right. Well, we'll keep our fingers crossed if
we can do it twice. Yeah. Well, tell us. About
the 7610 and what you found out with it compared
to some of the other radios that you've tested
and what do you think of it? Well, I'm impressed
with it and really the people probably want to
know how does it compare to the 7300. So of course
I've had the 7300 coming up on two years in April.
These courses 7610 was kind of delayed in shipment
or at least being sold in the US So it actually
arrived on a Friday The same time that the a
double RL 10 meter contest was starting later
that evening about whatever five o 'clock my
time So my wife was good enough to stay in town
in Denver and then drive it up here in the middle
of the afternoon on the Friday I was prepared
for it in this way in that I have three operating
positions here. So I had one of them empty, ready
to drop it in place and hook it up to an ACOM
1000. And it was ready to go and time for the
contest. Of course, the 10 meter contest when
it starts at 5 p .m. local time isn't open for
too long. So I think I got 45 minutes in and
mostly maybe exclusively CW. So I got to use
it all day, well, that limited amount on Friday
evening, all day Saturday. Unfortunately, I had
other conflicts on Sunday, but 10 meters was
even in worse conditions on Sunday than it was
Saturday, so I didn't miss much. The next contest
I ran was the W1BB Stu Perry on December 30th.
That's a CW contest. On the other end of the
band, 160 meters versus 10 meters. and actually
the week before that a double rail 10 meter contest
I ran the 7300 in the a double RL 160 CW contest
so I was using the those two radios kind of back
-to -back over that month and so it was a good
way to compare very good, so You you did some
of the the typical number crunching that you
do with receivers I assume and How did the numbers
turn out? Well the numbers were somewhat better
than the 7300 as you would expect and hope in
the standpoint of dynamic range. I saw an email
from a gentleman who had both of them and he
said he was so disappointed he was listening
to a weak beacon on six meters and he could hear
the exact same signal identically. on the 7300
versus 7610. And I'm thinking, yeah. I mean,
the noise floors of my two samples are within
1 dB of each other. And so 1 dB, we're talking
about sample variation of 1 dB, or laboratory
measurement of 1 dB. I mean, this is, quote,
in the noise. So one would expect them to be
able to hear. I mean, receivers today have no
trouble hearing, unless it's blown out or something
like that. So how did the numbers compare with
some of the higher end rigs? Let me bring up
my website here and all that so I can look at
it, but it's not at the top of the list, but
this is really because direct sampling radios
are vastly different from your legacy radio.
One thing I want to explain, people get out of
my website a lot and there's a lot of information
there. They sometimes get carried away and think
there's only one number in the world that you
should look at. And that's kind of crazy. And
I've mentioned that virtually every presentation
I've made from Contest University to all the
HamFest I've had the pleasure to speak at. You'd
need to look at the whole picture. But of course,
this table is sorted some way. You have to sort
it by something. And it's sorted by close to
end dynamic range, which is most critical for
CW pileups, de -expeditions, and contests. Now,
it's kind of funny that the top radio that's
been on my website since, well, 2014 was the
Flex 6700, but it was only on the top when the
preamp was on. And the league tested it a few
months later in the early 2015, and they got
the same result. The preamp made the legacy numbers
the way we measure radio's like for the last
40 years. It made it slightly better, even though
you really don't want to run the preamp on the
lower bands. That'd be crazy. But then I had
another sample that came in two years later,
actually in 2017, and I was testing it along
with the Ellicraft K3S, and for whatever reason,
turning on the preamp no longer made the numbers
a little bit bigger. So you'll see on my website
that the even though the K3 or the K3s didn't
change from testing it a few years later or on
this case on 10 meters because I was really trying
to compare the two and make apples and apple
comparison so We just have to consider that somewhat
of an anomaly doesn't mean there's anything wrong
with the 6700 it's just I just say take the number
with the preamp off is the number that you should
really compare so we've got the ICOM 7851 ahead.
Well, I would hope so. It's $13 ,500. The Hilberling
is ahead, but it's not really a CW radio. It's
mostly a sideband radio. So it doesn't have all
the features you'd want like QSK or really tight
selectivity even though they did drastically
upgrade it from a 500 Hertz filter to a 250 but
you know sometimes in a contest or a pile -up
you need to go down to 150 or 100. So the Hilberling
with crystal filters can't do that. And then
there's the somewhat anomaly and at the KX3 is
listed also fairly high but you have to consider
Read the footnotes. And if you look at its opposite
sideband rejection, it's a phasing radio. The
numbers are not all that high. So you just have
to say, OK, I have to kind of get a handle on
what the numbers mean and read the white paper
you can click on that explains all that. So where
did it come in? It had in the companion receiver,
you know, the R8600. Of course, it's a DC light
radio. They came in at the same numbers. at 98
dB for the close end dynamic range with IP+.
So really, I've said for a long time, if you've
got an 85, let alone a 90 dB radio, you've got
a good radio. There's approximately a dozen and
a half radios that are going to perform well
for most people most of the time. We don't stress
our radios to the max all the time. It's a good
thing because all those radios we had back In
the upconversion only days, that was like 20
years or more, starting with the TR7 and up through
like the Pro3, they were 70 dB radios, 7 -0.
And they were sort of OK on sideband and not
really adequate on CW, but that's all we had.
So luckily, I mean, if they didn't work at all,
you couldn't have bought them and you couldn't
have used them. So most of the time we can get
away with 85, 90 dB radios and the 7610 is one
of those. Okay, very good. So we've talked before
on the show about how you go through and do a
lot of those tests and everything. And you said,
like you were just saying a while ago, one DB's
difference at that point isn't going to make
a big difference in the world. It comes down
to other things that you have to consider. After
being able to use this for two contests and to
be able to kind of casually use it and You've
got the 7300 next to you and and I believe several
other radios including maybe a TS 990 What all
so what what's your opinion so far on? You know
picking one over the other Well, if you're a
CW operator and I'm glad you mentioned the 990
as you may or may not know mine took a nearby
lightning and electromagnetic pulse two years
ago and it was destroyed and It was a long story,
but my I gave it to my friend in zero qo who
can fix anything I think maybe could fix the
shuttle. I don't know the He fixed it with 40
hours of work and about $500. So I gave it to
him, but he's got a new QTH, doesn't have any
towers up. So I actually used the 990 in parallel
with the 7300 in the ARRL 160 contest the first
weekend of December. So that was fun going back
and forth. Well, the 990, of course, has got
solid state TR switching. It's got an audio peak
filter, and those are really important for the
CW operator. And this 7610 has solid state TR
switching, no clanking relays, and it has a great
audio peak filter, just like the 7700 had when
it was updated, and the ICOM 7800, and of course
the 7851. The ICOM really improved on their APF
some years ago. With some input from me, I'll
say. When you if you're talking CW More than
just casual operating I really like no relays
clicking and I like a solid state device keying
my linear Instead of a relay you can't do QSK
with a 70 300 at 30 words a minute forget it
so From that standpoint, the 7610 is a major
update for the CW operator. Now, if I just worked
sideband and I just was a rag sheaver, I'd have
a hard time justifying a $3 ,900 radio versus
a $1 ,200 radio. And even if you did sideband
contesting, the 7300 does a very good job. But
there's a lot more flexibility for the CW op
and the ergonomics are better just because it's
a bigger box and you've got all sorts of virtual
buttons that are on the front panel of the 7610
that require you to go into menus on the 7300.
So from an ease of operation, it's a big step
up also. Okay, so the advantages, of course,
you know, of the two receivers and then all the
extra real estate on the screen, the buttons
and everything make it a lot better. But as far
as actual receiver performance, there's one dB
difference. Well, there's more than that, but
it's still, either radio will do well most of
the time. I mean, you can always come up with
an environment where, you know, something is,
you know, maybe you stress the radio, but we've
got a 94 dB on one and 98 on the other. That's
with the IP plus on. With it off, you've got
81 versus 90. So it's significant, but most of
the time you'll never notice it. you know, the
more expensive radio has that feature. Now, you
mentioned, of course, the second receiver. We've
got Buwe Island coming up, and we know every
de -expedition works split. I don't care if it's
sideband, CW, I don't know what RIDDI guys do,
but we work split. So it's gonna be easier with
the dual receivers, of course. On CW, it'll probably
be up two or three, on sideband, up five or 10.
with the 7300 you got to poke a button and you
can kind of bop back and forth between VFO A
and VFO B but on the 7610 you've got two speaker
outputs or you can hook up your headphones for
stereo and get you know one receiver and one
ear and one the other you got separate volume
controls so you can balance them out that way
so for the in that case it's a big deal I think
in CQ Worldwide in October, I only worked split
on 40 meters for one station that I worked. It
was so little split going on that year, last
year in October, that I was stunned because usually
I work, I don't know, 10 stations on something
on 40 meters on, you know, the guy I'm working
his way down in the CW part of the band and I'm
up whatever frequency he's listening on. So I
would say on the average day, I would rarely
use the second receiver. I did play with diversity
this weekend, and it wasn't too exciting, but
it worked. I had two Yagi 200 feet apart, and
you could hear it kind of swirling around as
the QSB occurred, but it did knock your socks
off. All right. Well, we did give a chance for
everybody to send in some questions. on Twitter
and Facebook and we are recording this a little
bit beforehand due to Rob's schedule. So we kind
of did that last minute here. So we'll be watching
here and see if we get any questions coming in
from you all out there on Facebook or Twitter
here or Instagram. We'll be watching for those
as we go on. Okay, so that's part one and I'll
be back. With more with Rob Sherwood, NC0B, right
after this word from the National Voice of America
Museum of Broadcasting, right here on HamTalk
Live. The National Voice of America Museum of
Broadcasting located in Westchester, Ohio, just
north of Cincinnati, is only two minutes off
I -75. The museum is the former home of the Voice
of America Bethany Relay Station. Tours are now
available every Saturday and Sunday from 1 to
4 p .m. Eastern Time. You can see the control
room, a 200 ,000 watt transmitter, and the most
comprehensive collection of inventions by the
iconic Powell -Crosley Jr. Also on display is
a huge antique radio exhibit and R .L. Drake's
personal collection of most every Drake amateur
rig ever made. This is a unique opportunity to
see amateur radio in action and have a chance
to get on the air from WC8VOA. Admission is only
$5 a person. The museum is located close to historic
WLWAM and tons of shopping and restaurants. Take
a trip to the VOA museum or visit us online at
voamuseum .org. You're talking ham radio, baby.
You're listening to Ham Talk Live with Neil Rapp.
Ham talk lives on the air every Thursday night
at 9 p .m. Eastern time right here at ham talk
live comm Be sure to check us out on Facebook
Twitter and Instagram and we did post some links
that Rob's going to talk about in this next segment
up on our Social media sites and it's also in
the description of the show if you're looking
at that so you can get some links to some of
these numbers that he's talking about on his
website again his website nc0b .com and we'll
have some more about that later and then we're
going to take questions that came in on social
media in the past week we won't be able to take
any questions live since this is recorded so
my apologies for that normally that's what we
do here but we had to get this one recorded to
accommodate Rob. So we'll go back to the tape
and finish this up and then I'll come back and
answer some questions that came in and a few
announcements. But right now here's Rob. We're
talking to Rob Sherwood in C0B with Sherwood
Engineering talking about the latest performance
numbers on the ICOM 7610 and some other radios
as well. It's been good to hear some kind of
comparison between, you know, the 7300 which
made such a huge impact on things being the first
real SDR in a box. and the numbers were significantly
higher on it. And then now the 7610 comes out
with all the added features and just a little
bit more. So any other things that you've noticed
here on the 7610 that kind of surprised you?
Well, let me cover two things. One, you cannot
underestimate the effect that the 7300 had to
the world. I think they've sold something in
the order of 20 ,000 radios. I mean, this is
just unbelievable. The extremely popular K3 and
K3S has sold about 10 ,000 in eight years. And
here we've got a radio that's admittedly a whole
lot cheaper that's sold a staggering amount.
And what has it done? It's cratered the used
market. So if you want something that you just
couldn't quite budget for. And of all the radios
that come out, let's say in the last five years
or 10 years maybe, you can get something at a
bargain price if you're not going to buy something
new. So that's been amazing. The other thing
is, I think it had had to have had an effect
on what Flex offered or just showed at Dayton
this past year. Flex radio with knobs because
it became. Fairly apparent as you just said that
a SDR with knobs sold like hotcakes and I understand
that the 6600 M is maybe Began to ship as we
speak or within the next few days Somewhat later.
I'm sure than they hoped so the raid the 7300
was kind of a blockbuster as far as affecting
the market The other thing that we need to understand
and this is not very intuitive is that the direct
sampling radios, and I don't care whose it is,
we have to be much more conscious of how we run
our preamp, if we run it at all, and how we run
our attenuators. The legacy radios, if it's got
a narrow roofing filter, like, say, a K3. Well,
most of the time, 99 % of the signals don't make
it past the first mixer and the crystal filter.
And we've got, let's say we've got the preamp
off, the signal comes in the mixer, we've got
the 500 Hertz or whatever roofing filter, and
then that's it. So everything outside that roofing
filter isn't even downstream to get overloaded
or anything. Well, with the direct sampling radios,
this is totally different. It's kind of like
a roofing filter that's as wide as the whole
band, depending on whatever the... front -end
filtering is. And in this case, the 7610 has
a tracking preselector. It's only a one pole,
so it isn't dramatically effective. But on 40
meters, if you're on the low end of the 40 -meter
CW band, like 7020, and there's a broadcast station
at 7250 that's running a megawatt out of Europe,
well, the Did you select their tracking free
selector will knock that down maybe? 10 DB approximately
depends on where he is up above 7 .2 But if it's
a signal, but if you're on the phone band and
you're on 71 90 of course the tracking pre selector
isn't going to help So we have to watch our gain
our net gain, and this is not that obvious Too
many people say, well, I can't hear, so I'm going
to turn the preamp on, even if I'm on 40 meters.
And that's just crazy with anybody's radio. But
with the direct sampling, since it's so broad,
it may be receiving the entire handband and then
some. We have to be very careful that we don't
run the preamp when it's not appropriate. And
we run an attenuation. And people say, well,
if I run the attenuator, I'm not going to be
able to hear. And that is not true. if we use
some reason. If band noise is reading upscale
on your S meter, and certainly at night on 40
meters, what, if you're lucky if it didn't read
S7. Yeah, exactly. So turn the attenuator on
or the RF gain, whichever you like. I happen
to like the new feature on the 7610 that has,
you can adjust the attenuator in three dB steps.
You push on the attenuator button, hold it in
for like a second or two, and suddenly it goes
to a new mode, and you turn the multi -function
knob, and you can go 3, 6, 9, 12, clear up to
45 dB. I don't know what you do with 45 dB, but
I set it at 3, 6, 9, 12, 18, and so I can adjust
that attenuation so the band noise, instead of
reading S7 on 40 meters, it reads S1. And that's
what you'd rather like. Or maybe it reads as
zero. There's no reason for band noise to be
reading upscale, and it just makes it tiring
because whoever's talking pauses for a second
or you're in CW between words. And particularly
if you happen to like fast AGC, which I don't,
well, the band noise can be as loud as the guy
you're talking to. Why do you want that? Well,
I don't. Makes me tired. So if you can adjust
your attenuation so band noise is just below
AGC threshold, it's not going to affect sensitivity
at all. You're going to be able to receive just
as well and the band noise won't drive you crazy.
Very good information and glad to hear some of
that. Now some of the early reports on the 7300
The the IP plus that we're talking about here
some people were saying, you know Oh, you don't
want to run that on like field day when you've
got a bunch of radios around and you know and
some high noise environments it was just Really
bad. So this year at field day. We actually got
a chance. I was planning on okay I've heard I've
heard this said I'm not gonna use it and lo and
behold, yeah, we ended up going to the school
to do field day and here we are with the 7300
and so we tried it. In fact, we even turned on
the IP Plus just to see what would happen. So
what did you see? What did you observe? We didn't
have a single problem. Did not have a single
issue with the other radios right there within
a few hundred feet. Okay, so what band were you
on? Mostly 20 and 40 Okay, well, let me make
a comment on IP plus on my 7300 I never use it
period what I think it wasn't a great choice
of term because even though One should never
publish an IP 3 value for a direct sampling radio
because it has no meaning whatsoever And I think
the leagues finally quit doing that But IP plus
implies that it raises the overload point, which
it does not. All IP plus is, is dither. Now dither,
what the heck does that mean? It's just, if a
chip has dither built into it, then it can take
the low distortion products that are fairly weak
and probably blow band noise on the lower bands,
40, 80, 160. Turns the distortion products into
noise if the radio is done right which the 7610
is This 7300 was not it doesn't degrade the noise
floor much if you're on 40 meters I don't think
you would ever tell the difference with the noise
floor because the band noise is going to be high
enough Whether you punch it in or punch it out
waste of time but on the 7300 IP plus raises
the noise floor between 11 and 13 DB which on
10 meters you wouldn't want, 15 you wouldn't
want. The 7610, it only raises it about three.
And for instance, to compare the Perseus that
was the first direct sampling receiver I owned,
it only raises about two. So that's what you
expect. I don't think most of the time anyone
is ever gonna tell the difference whether they
got it on or off. So I just ignore it. But at
least it's there and it's done much better because
they did a better job with the clock. you know,
the clock oscillator in the unit on the 7610
than the 7300. So the fact that it didn't make
it worse, it didn't make it better, no big surprise,
particularly on 40 meters. Now, if you'd been
on 10 meters, you probably would have noticed
that you couldn't hear as well if it was the
weak signal. Okay, very good. And so you've noticed
that the 7610 definitely would do that better
than the 7300 on 10, 15? Absolutely. It only
degrades at about 3 dB. People should experiment
with it in a situation. They think they're kind
of being stressed and give feedback as to what
they see, but I doubt most people will ever know
the difference. I've never run it yet on either
radio, certainly on 10 meters. Conditions were
poor this year as they were last year. even worse.
And so strong signal overload is not an issue.
And so the last thing I wanted was to degrade
at all. And I certainly ran the preamp on 10
meters. And of course, on 160, what did I do?
I was comparing the, well, for the W1 BB contest,
all I ran was a 7610. Wasn't comparing it to
anything. But on the ARRL contest, the first
weekend of December, I was comparing the 990
with the 7300. The 990, I had the attenuator
on 18 dB. So it was comparable to the 7300 with
its only attenuator choice of 20 dB. So I had
to be fair. And that actually placed band noise
further below AG series threshold than I typically
run, but it was very wonderful from a... fatigue
standpoint. There was just no fatigue. And also
the noise reduction of both radios, the 7300
or the 7610, I like it. It's actually the first
two radios I've ever run noise reduction where
I liked it. So on 10 meter CW, I ran 3dB. I mean,
I ran it on three out of 10. It's adjustable
from zero to 10. And in 160 with its band noise,
I ran it on three on CW. So the Keeping noise
under control, band noise under control is really
important if you're going to be on the air for
10 -20 hours, let alone more than that. So that
was a very nice feature for both radios. All
right. Well, I've been checking here, and again,
we apologize for this being recorded to the listeners
and not having a whole lot of notice to send
in questions, but I'm not finding anything on
there. Well, we're wrapping this up, Rob. Just
anything else that you want to mention in your
runnings of the new radio since last time we
talked? Well, what's coming up, hopefully, for
CQ Worldwide 160 on January 26th is there is
a new Apache Anon. 7 ,000 DLE sitting in my home
in Denver. It came on Friday after I'd already
come up here at my contest station on Thursday.
So I will be grabbing that tomorrow, playing
with it in Denver. I won't be running it through
the lab yet. I'll just have to make it work.
And then I'll bring it up here next weekend and
get it ready to, I'll have one weekend to get
all the software sorted out. I mean, that is
the one thing that's. You only have to do it
once but you've got to get it set up to use an
external tuning knob because I don't like to
tune with the mouse Get it to n1 mm plus to work
with the radio to talk to each other get it to
key the linear and all that stuff and So that's
the plan for the next two weeks is to get ready
for the Apache All right, well we'll be looking
forward to hearing more about that and I appreciate
you taking the time to come on the show and get
this recorded for us and been anxious to hear
what your response is on that 7610 because it's
a mighty good -looking radio. Let me mention
one thing that's been kind of a glitch and it's
probably like 99 % sure it is a software issue.
Some people have had issues with the main receiver,
just those dead and they have to punch a button
or power cycle it, and the mothers have had a
tone come on and the audio goes dead except for
a tone. I'm sure ICOM's working on that. I haven't
seen it. I don't imagine most people have, but
if you are on the 7610 Yahoo Reflector, there
is half a dozen or a dozen people that have been
frustrated. So this is a... software -defined
radio. This is totally different. See the 7300
used pre -existing software from like the Pro
3 and so they didn't have to write code from
scratch, but this radio has a field programmable
logic array like some of the other and maybe
probably all the other the Apache or the Flex
or whatever and so ICOM had to write code that
was from scratch. And so if there's a bug or
two, no big surprise, that's why it's upgradable
with a little SD card. Yeah, and that's a whole
lot easier than trying to change out a bunch
of components. We like that little SD card upgrade.
Yeah, or like on an NRD 545, you had to pull
out chips that were the size of your thumb and
plug new chips in. Well, that's passe today.
Well, it sounds like it's pretty well under control
and hopefully those folks that are having trouble
with it will get a software upgrade soon and
that will take care of it. Again, Rob, thanks
so much for coming on the show and sharing your
results with us and we look forward to talking
to you again soon about some more. All right.
Well, I'm glad we could work it out. here and
even if it'll be recorded, hopefully they'll
enjoy it. Thank you. All right, so if you're
interested in seeing this data, again, it's available
online at Rob's website. That's NC0B .com. And
if you're interested what all these numbers mean
and how Rob gets all of the data, check out HamTalk
Live episode number 29. Just go back in the archives
at HamTalkLive .com or on the podcast version
and you can see how he comes up with all these
numbers. So we do have a couple of questions
that came in throughout the week after we recorded
this and Rob was good enough to answer by email.
So the first question was from Dr. Scott Wright
K0MD and he asked why do you think the DR3 is
substantially lower than the Flex SDRs design
or chip factors maybe and what did you measure
RMDR at? And Rob's response was that They're
not really. The Flex 6700 that he tested in 2014
and ARRL tested in 2015 measured higher with
the preamp on than off. And no one knows why,
including Gerald Youngblood, the man who started
Flex. When Rob tested the second sample of the
6700 in March 2017, it was no longer the case.
And when the League tested a 6500 in February
2017, again, no longer the case. So look at the
preamp off number for Rob's test in 2014 on the
6700 and it's 99 dB. In 2017 the more recent
sample was 99 with the preamp off and 96 dB with
the preamp on instead of 108 dB with the preamp
on. He did have a footnote in 2014 saying that
the data does not imply you should generally
run the preamp. It's just a testing anomaly of
direct sampling receivers. So there's a minor
scatter of data with several direct sampling
SDR radios. The Apache Anon 200D is 99 dB. The
Percy is 99 dB. The 7610 from ICOM is 98 dB with
the IP plus on. The ICOM R8600 98 dB with IP
plus on. The Flex 6700 in 2017 was 99 dB with
the preamp off. 96 with it on. The Flex 6500
that ARRL tested in 2017 is 102 dB with the preamp
off, 100 dB preamp on, and the IC 7394 dB with
the IP Plus on. And as far as RMDR goes, at 2
.5 kHz it was 112 dB, 5 kHz 115. 10 kilohertz
119, 15 kilohertz 121, and 20 kilohertz over
122. And there's some links that we put in the
social media and on the notes on here about these
radios. So if you go to nc0b .com slash 70 300
or slash 7610 or slash 8600 or slash 990. You
can see some of those comparisons in the 990
one does a comparison of the 7300, the 7610,
and the 990 in contest. The other question that
came in was from Carl KD9HQT. Want to know how
accurate the digital meter is on the 7610 compared
to a traditional analog meter? And Rob says it's
S9 with the preamp off. negative 73 dB and 50
micro volts. Above that the S meter is very accurate.
Below that an S unit is about 3 dB and closer
to 2 on the low end. With the preamp on it's
about negative 80 dB, 23 micro volts and all
that's at nc0b .com slash 7610. It also mentions
that if the R8600 was set to DBM instead of S
units, it's very accurate in any signal level
with preamp or attenuator setting, but too bad
the transceiver doesn't have that option that
could be in the firmware. Well, we're just about
out of time. I want to mention the AM Rally.
We'll talk about it later. It's coming up on
Saturday, February 3rd. I also want to mention
Contact Sport. The audible version is getting
ready to come out. I talked to 3BB and said it's
all ready to go. And the Young Ham Lens Hand
Award nominations are out there. If you know
somebody 19 or under, you can nominate for that.
We'll be talking about that later. Next week
we hope to have Bouvet Island on live. We're
going to be talking Bouvet Island next week.
So seven three seven five and may the good DX
be yours.