On the issue of buffering the IF output of a radio. If you tap into
the RF segment of any radio it is important that you buffer the
output, not only to minimize the possibility of "Zapping" the radio,
but also because you will load the signal path and reduce the signal
sent to the next stage. This also applies to discriminator outputs so
you don't loose half your signal or more.
When I mod a radio to tie into an IF or discriminator I prefer to use
a high impedance coupling and not to over amplify the signal, and/or
use a shielded mini-enclosure. If the mod is going in to one of the
large radios like a R-9000, R-8500, R-7000, PR-700, MSR, that you are
going to be using for sweeps then you can through in a little extra
amplifications and then split the signal by 2 or more and drive
multiple output devices like TWO spectrum displays, or an
oscilloscope, a demodulator, and two spectrum displays all at once.
Instead of rolling my own, I would like to see is someone come up
with a off-the-shelf clean buffer circuit that gives you three
separate high impedance inputs, that amplifies, and divides to four
channels each for a total of 12 outputs. This way you can drop it
into pretty much radio, and pick off whatever combinations of signals
you need to look at.
The R-1500 is a bit crowded inside, and the surface mount components
require a delicate hand. Even with the tight quarters it is a great
radio to modify but those limiter diodes on the front end create most
of the birdies. The switching PIN diodes also are not the cleanest
and most isolating they could have used but a couple of diode mods
will drastically reduce birdies and inter-modulation distortion problems.
-jma
At 07:35 PM 3/24/2006, cont..._at_yahoo.co.uk wrote:
>For your Icom PCR-1500 information you may want to check:
>
> http://groups.yahoo.com/group/ICOM-IC-R1500
>
>If you need a 10.7 Mhz IF-output on the spot
>i can do it for you at 200 US$ (excl transport)
>Problem might be that i'm in Europe,
>instead i could supply a new one that
>i buy here and add the 10.7 Mhz output to it
>and then send it to you.
>
>[snip]
>
>If you want i could also add a 450 Khz output to it
>wich could be usefull for other things like for example subcarrier
>demodulation.
>
>Adding additional outputs is more then just adding a wire
>..if done bad it will cause additional birdies on your scanner
>..if not buffered it might zap the IF-signal and cause other problems.
>
>
>contranl
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Received on Sat Mar 02 2024 - 00:57:21 CST
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