Frequency stability and Icom, Yeasu, Kenwood radios
Larry
I did not intend to dis Icom radios in general when I made the original
statement. In fact, I think a great deal of most Icom products
especially the IC-746/IC-746 PRO. The fact is that most (not all) Icom
radios in common VHF/UHF use have this annoying idiosyncrasy.
Some history; when it became necessary for me to get a new radio for my
VHF/UHF work, I looked at them all. First on my list was the 746. After
some discussion with my EME buddies, I learned that the 746 in
particular had a *slight* drift problem that would diminish the WSJT
decoding sensitivity. Since I was primarily interested in using that
mode for EME I looked further and found that the EME crowd was migrating
toward the TS-2000.
Now I don't really like the TS-2000 all that much. It is overall not as
good a radio as the 746 series or the FT847. However, it comes stock
with an outstanding TCXO and a digital mode interface that is second to
none. For WSJT EME and M/S work there is no better radio. However if
your thing is SSB/CW only, I would recommend that you stay far away from
the TS-2000. It's simply a matter of selecting the best tool for a
specific job.
The real issue is short term stability, specifically during TX 1-2
minute periods. The Yeasu FT-847 is very good, as is the FT897/857. The
TS-2000 is outstanding with drift during TX on the order of 1-2 Hz
typically. The IC-746 on the other hand shows drifts of as much as 100Hz
during a 2 minute key down TX period. If you install the TCXO option
that improves quite a bit but is still not quite good enough for EME
work. I can tell a guy is running a IC-746 in the first 15 seconds of
his TX by watching the waterfall display! With the TCXO, they always
drift 20-30 Hz and that's just enough to degrade WSJT sensitivity by
about 2-3 dB even with AFC. It won't keep you from making contacts, but
will limit your success, especially if you have a small station.
If you do a web search, you will find a few people have come up with
fixes for this problem, I think one might be AA4MY? It's not real hard
but it is a pain in the butt and not for the faint of heart.
BTW a real sleeper is the FT-897. It works extremely well for the
digital modes for a 800-900 dollar radio. The interface sucks compared
to the Kenwood, but it is serviceable and the TCXO is good enough to not
cause any problems.
I have used my FT-897 for RTTY, M/S, and JT tropo on several bands would
great results. I now use my FT-2000 for EME and M/S on 6 meters and my
TS-2000 for most digital stuff on 144/432 and sometimes 50. The FT-897
does digital on 222 and 1296 at this time.
Hope this helps.
73, Larry
--
Larry - W7IUV
DN07dg
http://w7iuv.com
Edward Cole
More and more I am glad with my choice of the FT-847 back in '99. I
did get one of early ones clobbered with birdies but a trip back to
the factory improved that considerably. It is my "workhorse" radio
doing HF, eme, ms and IF for UHF/mw bands. In a very implusive
moment a couple years later I bought the original FT-817. Again, I
have been pleased with it. It had done some satellite and mobile
operation, and the main radio for mw portable (and often rides in the
briefcase for trips and used with rental cars). One particularly
impressive discovery was that the Packet jack is pin-identical on the
FT-847 and FT-817. The FT-817 has sw modulation adjustment for a
whole slew of modes including AFSK, FSK, and PSK.
Both seem fairly stable in frequency just from subjective use
on-air. On eme I have run JT44/JT65 since 2003 with over 115
stations worked on the moon. None have complained about freq.
stability. On the local 2m SSB net the Icom guys are always off
freq. Yet my stock Yaesu's agree with each other with 10-Hz
(resolution of the dial).
I have WSPR-040 loaded and it runs, but I have yet to do much with
it. I guess I could try it on 30m (receive on my 40m dipole).
Happy Easter from Alaska.
Ed - KL7UW
W7CE
http://www.chris.org/Modifications/IC-746-almost-free-tcxo.html
Basically, cotton balls are used as insulation around the 30MHz reference
oscillator and frequency doubler to minimize the effects of the TX only fan
blowing air over them. I decided to check the 2M frequency drift during
transmit on my IC-746 drift using an FT-736R for the receiver and SpecJT.
After an overnight warm-up of both rigs, I tried to emulate the key-down
sequences of WSJT by hand - key down on the 746 from 2 seconds to 48 seconds
(I think that is right) on the even minutes. The first sequence had the
most drift with about 20-30 Hz drift up in frequency. Subsequent sequences
showed about 15-20 Hz drift, most of that in the first 15 seconds. I had
the power set higher than I would normally run into the amp (about 60W), so
the drift may be somewhat less when I cut the power back to 25-35W.
Then I reversed rigs and transmitted the same sequence on the FT-736R. As
far as I can tell from the SpecJT screen, there was no measurable drift on
the 736R, just a nice vertical line. So, in the short term, I'll be using
the 736R which has just enough power to drive my amp to 500W. In the long
term, I'm going to build an external 30MHz reference oscillator to feed into
the 746. Looking at the schematics and service manual, it appears that all
internal LOs are derived with PLLs or a frequency doubler from the 30MHz
reference oscillator. I'm currently gathering parts to build a GPS
disciplined 10MHz oscillator and then I'll use that to drive either a PLL or
a frequency tripler to get the 30MHz reference. I'll probably add an
internal relay to the 746, so the rig will still work standalone when
desired.
Also, Tigertronics shipped my SignalLink USB yesterday and it's scheduled to
arrive tomorrow, so I should be QRV tomorrow evening.
73,
Clay W7CE
N7SC
Is your rig the non pro IC-746 and do you have the CR 293 installed ??
73...Steve
W7CE wrote:
> A couple of weeks ago I added the following very simple mod to my IC-746:
>
> http://www.chris.org/Modifications/IC-746-almost-free-tcxo.html
> 73,
> Clay W7CE
>
>
>>
>>
>
>
> >
>
>
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W7CE
I have the plain vanilla 746 with the stock 30MHz XTAL local oscillator.
73,
Clay W7CE
----- Original Message -----
From: "N7SC" <n7...@charter.net>
To: <w7...@curtiss.net>
Cc: "PNWVHFS" <PNW...@googlegroups.com>
Sent: Thursday, April 17, 2008 5:00 PM
Subject: Re: [PNWVHFS] Re: Frequency stability and Icom, Yeasu, Kenwood
radios
Greg Chartrand
It costs between 60-$70 where the CR-293 runs $140-$240. Big difference!
Greg
W7CE <w7...@curtiss.net> wrote:
Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now.
W7CE
Chartrand - W7MY
Richland, WA.
DN-06IF
W7MY Home Page:
http://webpages.charter.net/w7my/
n7...@charter.net
Tnx for the reply. Sorry I misquoted the CR-282 as the CR-293 which is for the IC-910H. I also didn't realize that the 746 Pro used a different osc frequency !
> Greg Chartrand - W7MY
> ------------------------------------------------------------------------------
Kevin Imel
N7SC
The CR 282 is an easy install in the 746. Texas Towers has them for
$119 on their website...if it's current !
73...Steve
kb7...@donobi.net
with a 10 MHZ reference... or at least provide an external 10 Mhz
reference input!!! That would be "too easy" I guess...
Eric
KB7DQH
Edward Cole
73 Ed - KL7UW
W7CE
working with the FT-736R about 15 minutes before moonrise. At 0227 I got a
report from DL8GP that he was copying me at -27 (I was calling OK1TEH). No
contact was made. However, later I was able to complete my first EME QSO
with Mike, K6MYC. Mike's best here was -23 and my best at his end was -20.
A couple of other stations were also able to copy me while I was working
Mike.
I haven't had a chance to fully evaluate the SignaLink USB, but so far so
good. The only problem I had was a loose wire in the cable to my 736R.
I'll open it up tomorrow to take a look. And now it's bedtime. Moonset is
in a few hours.
73,
Clay W7CE
.
Bill W5WVO
External Reference Module (plug-in) is finished and available. You will then
be able to lock the K3 to a GPS-disciplined oscillator or other high-accuracy
10 MHz source. No date on the availability of this optional module, but we
have it from Elecraft that it is "on the list".
Bill W5WVO
Lynn Burlingame
the individual development of accessories. A nifty feature like this is
going to cause other manufacturers to fish or cut bait!
Lynn
N7CFO
Bill W5WVO
--
No virus found in this incoming message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 269.23.2/1386 - Release Date: 4/18/2008
5:24 PM
LANCE COLLISTER
cn85be
Did Mike find some time to sell you some hardware? He built some of my
ruggedized H Frames and some of the antennas here....
Jeremy w7eme
W7CE
this, although also a little disappointing that it was so easy with JT65.
I'm currently using an 18MXXX. I don't think it will be too long until I
have a pair of XPOL antennas from M2. I have an M2 MT-3000 EL rotor also,
but I think that the smaller MT-1000 is more suitable for my current needs,
so I may be ordering one of those as well. I talk to Mike pretty regularly
on 75M, and will see him at the Visalia DX Convention next weekend. I'm
sure he'll sell me something before the weekend is over.
I got up early for moonset and worked JH0MHE this morning. I can tell that
my sleep pattern will be broken for a while ;-)
73,
Clay W7CE
LANCE COLLISTER
addictive!
W7CE wrote:
> Thanks Jeremy. It's pretty gratifying after waiting almost 40 years to do
> this, although also a little disappointing that it was so easy with JT65.
antennas (10 dB) or MORE to have the same success as with JT65. And you proved
that it is very easy to get the hang of (15 minutes!). Most of the people who say
they don't have time to learn how to use it just have no interest in doing
anything except CW, because I am sure ANYBODY who really is interested in working
DX can squeeze 15 minutes out of their busy schedule ;-)
However, if you don't think 2m EME with JT65 is enough challenge for you, we would
certainly welcome you to 6m EME ;-) I guarantee you would find that more
challenging. Whereas I almost always hear a station's JT65 tones (-22 dB or
stronger) on 2m EME, I almost never hear the tones when I complete with stations
on 6m EME.
>
> I'm currently using an 18MXXX. I don't think it will be too long until I
> have a pair of XPOL antennas from M2. I have an M2 MT-3000 EL rotor also,
> but I think that the smaller MT-1000 is more suitable for my current needs,
> so I may be ordering one of those as well.
array is PERFECTLY balanced. I have talked to too many people who have been
through 2, 3 or more of the MT-3000 elevation systems trying to find one that will
stand up to their arrays.
I talk to Mike pretty regularly
> on 75M, and will see him at the Visalia DX Convention next weekend. I'm
> sure he'll sell me something before the weekend is over.
>
> I got up early for moonset and worked JH0MHE this morning. I can tell that
> my sleep pattern will be broken for a while ;-)
>
> 73,
> Clay W7CE
>
--
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
P.O. Box 73
Frenchtown, MT 59834 USA
QTH: DN27UB
TEL: (406) 626-5728 URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11, 6m DXCC #815