[AMRadio] Getting started


Brett Gazdzinski Brett.Gazdzinski at verizon.net
Tue Feb 24 20:58:17 EST 2009


I liked the R390a best of all the receivers I had, from the operating 
standpoint.
It was stable, accurite, had a good IF out for the scope, detector output, 
muting.
You did not have to guess the frequency like most other vintage receivers.

It did tend to break clamps on the gears, but other than that, I never had 
to do anything with it for 20 years of heavy use.

It was a bit noisy, but not bad, jumping between 160 and 10 meters was not 
something you would do often on that receiver, even 160 to 40 was a workout.

Its big, heavy and rackmount, and now, expensive.

The NC300 or 303 was also good from what I remember, although not my idea of 
a nice looking radio.

I thought the 75A4 was very poor on AM, but looked great.

I always thought something like a 75S1 could make a good AM receiver with 
some work.

An sx101 might be good, I had a Drake R4c, to narrow for AM, if people were 
off frequency, you could not hear them at all....and people seem to be off 
frequency on AM a LOT!


I sold the R390a and built my own receiver, which on 160, 80 and 40 meters 
works much better than the R390a.

A good AM receiver is really very simple, unless you want it to do all 
bands.

For 160, 80 and 40 meters, you do not need any sort of RF amp stage, a 
simple high Q link coupled tuned input works great, a LO and mixer, 2 stages 
of IF amplifcation, a hifi detector, some AGC, an S meter amp, and a 455KHz 
xtal osc for a bfo.
I used kiwa filters, which work like Collins mechanical filters, and a 
digital freq counter with a 455 KHz offset that reads the actual frequency.

So its small, light, accurite,stable, low noise, hifi.
You can also do tricks so when you change bands, the receiver is tuned to 
1880, 3880, and 7290.

So far, I have not found a receiver that sounds better on just AM, no sync 
detector or anything fancy, but its better than the sdr-iq was, or the icom 
pro3, r390a, etc.

Brett
N2DTS

 



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