I am not sure if the capacitance of the power diodes would be too high. This
could cause poor isolation, but if you reverse bias the unused filter
diodes, they might work.

Pete

wrote in message
oups.com...
Thanks for the info and advice Pete. I recently saw a comment that
standard 1N4002 type (60 Hz) diodes are actually good replacements for
the PIN diodes on the front-end band pass switching networks. Have you
heard of this?

Frank

Pete KE9OA wrote:
Hi Frank,

That is a nice receiver, and the mods that you have done seem to cover
everything. The only thing that I can recommend....if this receiver uses
diodes to switch the input bandpass filters, I would replace them with
1N5767 PIN diodes. Bias them at around 60mA. I think that you can run up
to
around 90mA, but that might be pushing them.
Philips also has some suitable PIN diodes, but you want to make sure that
you have a long enough minority carrier lifetime.
Congratulations on the new receiver! I haven't picked up anything new for
awhile, except that NRD-91.

Pete

wrote in message
oups.com...
Hi Pete; I just recently acquired an essentially mint Icom R70 off of
Ebay. It has the 500 kHz CW narrow filter included and came with the
manual and original box. After using this radio for a couple of weeks
I'm very impressed short of the weird ergonomics and the end of band
tuning anomalies. The sensitivity and selectivity are superb and the
BP shift and IF notch are among the best I've used. The audio is a bit
on the shallow side but I replaced a few of the electrolytic coupling
caps with film caps and the difference was very noticeable. I also
removed the LW/MW input attenuator and disabled the input rf amp defeat
for MW/LW. It can now be switched on and off from the front panel
switch. What is your experience with this radio and are there any other
improvement modifications that you know of?

Comments on this receiver from others are welcome.

Frank
K3YAZ
Tucson