[Yaesu] FT-1000MP: main rx AF hiss - Thanks
tgstewart@pepco.com
tgstewart@pepco.com
Thu, 18 Dec 1997 08:40:17 -0500
I havent had time to follow this thread carefully, but I think all of you
should have your radios carefully realigned before you start redesigning
the radio. The MP is a very complex radio with no firmware documentation
or in depth alignment instructions (even the service manual is cursory).
For one thing, there are adjustments for RX gain by band in the hidden
menu. I dont have the info or radio in front of me, but I know they are
there although I dont recall if it's IF and/or RF that it adjusts. Another
strong argument that I would have is that I think some of these radios are
poorly aligned or have drifted due to no burn-in time. A simple
realignment of the radios oscillators, IF coupling transformers, etc., may
cure some ills.
I have 2 MP's and I have realigned one of them which improved IF responses,
IF shift centering, and TX passband response. The other (newer) one I
havent done yet and it definitely does not work as nicely as the older one.
IF Shift goes off center on narrow filters, the TX passband is off center,
and the RXer just doesnt sound as good. When I get a chance this winter,
I'll go through that one as well. Note that the most important adjustments
you can do with just a good frequency counter and signal generator
(hopefully calibrated). Adjustment of the radio through the software
(offset oscillators, stage gain, etc.) should be the last resort. Using
the radios offset settings to correct a basic alignment problem is a big
mistake...same with the gain settings.
Beyond the radio being aligned and functioning correctly as designed by the
factory, it's important that the operator know how to get maximum
performance out of a receiver, and basic tests to check for weak signal
capability. One of the most important tests is to make sure you have
adequate front end gain on the upper bands. With an antenna connected, you
should be able to hear a significant drop in noise level when you select 6
db of attenuation or perhaps the B antenna port if nothing is hooked to it.
If you dont then you need to increase RX gain until you do. On the MP the
worst case band is usually 15 meters at night. Make sure that the IPO is
NOT lit, RF Gain is at maximum, and you have selected wide filters. If
it's still too low, try realigning the RX. Lastly, you can try tweaking
the gain setting in the hidden menu for that band. On the lower bands,
gain is not important, it's overload/dynamic range that are important.
Here's the guideline: Select as much attenuation as needed to keep the
atmospheric noise well above the noise floor, but no more. Below 7 mhz,
run the radio in TUNED mode as long as your band noise will stay out of the
noise floor. These 2 steps are usually more than adequate, but you can
also turn down the RF GAIN control as necessary. All of these steps will
maximize effective dynamic range ie. guard against front end overload while
preserving weak signal capability. Lastly, make sure you dont use your
noise blankers unless absolutely necessary as this will screw up your
dynamic range and effective selectivity.
>From my experience with the FT1000 line, the original 1000 needs more gain
on 15 and 10 meters. My recommendation would be to have an RF preamp you
can switch in line to get signals out of the noise floor. The MP's have
plenty of gain on 10 meters in the TUNED mode, but 15 and perhaps 20 can be
a bit marginal on a dead band. You may be able to correct this from the
hidden menu gain settings. Otherwise you could use the same RF preamp
trick. Again the test for gain is to check for noise levels decreasing as
you select attenuation, or just disconnecting the antenna. If I still
owned my 1000D's, I'd put the RF preamp in line. On the MP, it's probably
unnecessary although it may help 15 meters a tad.
Someone suggested that the MP had a "wide band" front end. This just aint
so. It's one of the best, if not the best front ends available on the
amateur market.
I would strongly discourage anyone except a practicing engineer with proper
test equipment from modifying the MP internally. Even if there is some
reengineering that could improve some spec., I guarantee it's going to be
a very minor improvement...one you probably wouldnt be able to notice on
the air. On the flip side of that, you run the risk of really screwing up
your radio if you arent real technically inclined and certainly voiding any
warranty is an issue.
Another caveat is that just because your radio recently came back from the
factory, dont assume that it was aligned correctly. When my older MP went
to Yaesu for updates it came back all out of whack. Instead of adjusting
oscillators, a couple of the offset software settings had been tweaked.
It sounded horrible on the air. After a hardware realignment and a master
reset to clear out whatever they had done to it, it worked great!
73, Ty K3MM
wd8arz@null.net on 12/17/97 02:51:42 PM
To: yaesu@contesting.com
cc: 1000mp-list@jehosophat.com (bcc: Tyler G Stewart/BENN/CEC)
Subject: [Yaesu] FT-1000MP: main rx AF hiss - Thanks
Hello George, thanks for posting again about the work your doing into the
IF signal to noise ratio modification for the FT1000MP. I am following
your comments with great interest and would be glad to put one of your
boards to a test on this end......and return the board to you if you wish
with the results of that test.
With the broadband nature of todays radios, I would be concerned about
increasing front end RF/IF gain in the presence of local strong
transmitters. I seemed to remember one of the goals set for the design of
the FT1000MP was to improve performance in just this area, and to keep
distortion and overload situations to a minimum.
I am concerned that not every radio will behave well with a modification of
this type and would be very eager to hear from Yaesu their opinion as to
the benificial gain this will bring to the 'overall performance' and any
trade offs to their design goals. I would be disappointed in Yaesu if this
is actually a flaw in their design for a rig in this performance and cost
range. It would be should a basic error to defy their engineering
resources.
At the least, those making this modification will need to realign/calibrate
the entire radio to put the S meter and dymnamic performance objectives
back into optimum, but my biggest concern would be the performance factors
in strong RF field areas.
Your input is greatly appreciated and I am looking forward to any and all
modifications for refining this terrific transceiver.
73 from Bill - WD8ARZ
E-Mail Reply to:
wd8arz@null.net
----------
> From: George Cutsogeorge <w2vjn@rosenet.net>
> To: Steven J. Franke <sfranke@uiwpls.ece.uiuc.edu>; yaesu@contesting.com
> Cc: sfranke@uiwpls.ece.uiuc.edu
> Subject: Re: [Yaesu] FT-1000MP: main rx AF hiss
> Date: Wednesday, December 17, 1997 1:40 PM
>
> Hi Steve and the list,
>
> Some time ago I posted a message about the "audio hiss" which answers
some
> of the questions that have recently come up. The previous msg is
repeated
> below. Since that time I've built a prototype and run some dynamic range
> tests on the modified receiver. The net effect due to the increased
> sensitivity is actually a small increase in dynamic range. Yaesu was
kind
> enough to sell me some connectors and cables, so I am laying out a PC
> board.
>
> George, W2VJN
>
> ----------
> 11/24/97
>
>
> I have been looking into the problem and have what I believe to be a good
> solution. The noise coming out of the receiver is mostly IF noise. This
> can be verified by removing a pair of filters, one in each IF, and
> measuring the audio output noise and setting a reference on the meter.
> Then, return the filters and take another measure. Any additional noise
> will be coming from the front end of the radio. The front end noise must
> over ride the IF (and audio) generated noise or the receiver noise floor
> will be degraded. The result of my test showed from 0 to +2 dB of
> additional noise with various filter combinations. This is not enough to
> over ride the IF noise and shows that the gain before the second IF is
too
> low.
>
> The RF gain reduces the noise because it operates on the agc buss which
> reduces the IF gain as well as the RF gain. Another way to observe the
> problem is to switch in front end attenuation. You will notice that the
> noise heard out of the radio does not reduce very much. If the noise
were
> coming from the antenna, attenuation would reduce it. This is not a
> problem on 10 meters when the tuned front end is employed as the dual
gate
> mosfet has more gain than the push pull RF stage used on the lower bands.
> You will notice more front end noise on 10 meters for this reason.
>
> In my unit I have installed a small, high dynamic range amplifier with a
> few dB of gain at the 70 MHz input to the IF board. It doesn't take much
> gain to over ride the IF noise and excessive gain would reduce the strong
> signal capabilities of the radio. The measured noise floor of my radio
has
> improved 3 to 4 dB and it really sounds good to me now. Antenna noise is
> very apparent and I have been able to reduce the IF gain using menu item
> 9-1 by about 3 dB. This further reduces the IF hiss problem by an
> equivalent amount.
>
> After the WW contest I'll measure the dynamic range of the modified radio
> and maybe adjust the gain a bit.
>
> The amplifier is very simple. A major problem is that I have not found a
> supplier for the pc mounted coax connectors used in the radio. If I can
> come up with connectors, I intend to make a mod kit available through
> International Radio.
>
> George
> w2vjn@rosenet.net
--
FAQ on WWW: http://www.qsl.net/k7on/yaesu.html
Submissions: yaesu@contesting.com
Administrative requests: yaesu-REQUEST@contesting.com
Problems: owner-yaesu@contesting.com
Search: http://www.contesting.com/km9p/search.htm
--
FAQ on WWW: http://www.qsl.net/k7on/yaesu.html
Submissions: yaesu@contesting.com
Administrative requests: yaesu-REQUEST@contesting.com
Problems: owner-yaesu@contesting.com
Search: http://www.contesting.com/km9p/search.htm