I have had all three of these receivers............the 7700 is nothing to
write home about, while the 8800 is just ok. Even though the 8800 uses a
doubly-balanced diode ring for the 1st mixer, the LW band is awash with MW
spurs.
It makes me wonder what method this person used when he made these IP3
measurements. What was the level of each of the tones, and what was the tone
spacing? With wide spaced tones, the FRG-7 should be better since
preselection would protect the front end a bit.
Another little known fact.............the early versions of the FRG-7 that
didn't have the fine tuning control had a better IP3 since the gain
distribution was better. Later models of the FRG-7 were more prone to
intermodulation since the RF amplifier/mixer stages appeared to run at
higher gain. Remember the input IP3 is degradation is directly proportional
to the gain ahead of the 1st mixer...........also, the RF amplifier is also
prone to IMD effects. I believe that a 3SK40 dual-gate MOSFET was used in
this application.
About that mechanical filter mod.................how are you able to avoid
signal feedaround with the board layout in the FRG-7?
One way you could avoid it is through the use of shielded cable with its
30pF/ft capacitance. No matter what approach you take, there will be
compromised performance. In order to take advantage of the 120dB ultimate
rejection of a mechanical filter you really need to have ground flood on the
circuit board that would really isolate the I/O pins of the filter. You are
not going to get that kind of rejection with that board layout. Also, even
if the board layout could support a mechanical filter (which it cannot) why
would anybody want to waste any money on such a device when the radio has
such limited dynamic range?
In conclusion, early versions of the FRG-7 had fairly good dynamic range
while later versions that had the fine tuning control had similar IMD
performance to the Radio Shack DX-300. So take your choice..............the
FRG-7, the problem laden 7700, or the 8800 with is poor IMD performance on
the LW band. I would surmise that the poor performance of the 8800 is
because Yaesu probably chose to use common switching diodes in the front end
instead of using PIN diodes.
It is also interesting that this reviewer rated the FRG-8800 as having
better sensitivity than the FRG-7. Was this person measuring all of these
receivers at the same time, and was he using hard or soft measurement
techniques? What frequency did this person make these measurements at? Were
they all done at the same frequencies? Was the same signal generator being
used, and if so, what was the model number/manufacturer of the generator?
Take a look at the one of the "useful" I.F. bandwidths of the 8800. The wide
bandwidth has a very poor shape factor. Another thing to consider is not
only the 6/60dB curves, but also the ultimate selectivity. Many things to
consider when presenting the "proof".

Pete
"mike maghakian" wrote in message
...
I thought I would dig up some numbers to back up what I have said for
years, the FRG-7 is grossly over rated.
These stats are measured in the lab of the great Ranier Lichte in his
awesome book "radio receiver, chance or choice" the best review book ever
written in the history of shortwave radio. In fact I just modified one of
my copies to make it easy to scan reviews to mail to people for proof of
what I say.

FRG-7 FRG-7700 FRG-8800
SW sens (uV) 2.1 2.1 1.1
3rd order ICP (dBm) -25 -10 +3
selectivity (-6/60) 3.2/8.8 *1 3/7 + 7/18

*1 Wide 11/26 Norm 5.2/13.5 Narr 2.6/8.2

In every category of these most important specs, the FRG-7 loses. In fact
the 3rd order ICP is pretty BAD !!!!!!

The facts speak for themselves, the reputation of the FRG-7 is not based
on reality but fantasy.

I am not crazy about the selectivity of the stock units of any of the
FRG's so my FRG-7 and my FRG-7700 both have mechanical filters and the
7700 has an upgraded ceramic as well. But the 7 selectivity is way too
limited for the real world !

And the 7700 and 8800 both sound really NICE !!!!