The AM Forum

I've always been curious how boat anchor receivers stacked up in terms of minimum discernable signal (MDS), blocking and two-tone dynamic range so I made  measurements on some of the highly prized receivers 'of the day'. Turns out they did pretty well!

Results: http://www.w1vd.com/BAreceivertest.html (http://www.w1vd.com/BAreceivertest.html) 

Great info. Thanks Jay. Your words on the excessive gain exhibited by these receivers is also worthwhile. I've found that over they years I've tended to operate most older receviers with the RF gain backed off because I could still hear everyone on frequency but the background noise far was less. Now I see I also got a little better DR too.

What bandwidth(s) were used?

Where's our SS-1R?

Very cool Jay. How about 2 KHz spacing for a laugh.
The cool thing is you can reduce the RF gain and not hurt DR.
No wonder everyone thought early SS RXs were junk.

Hi Jay:

Thanks for doing all the work!

I always thought the HRO-60 did not have as much dynamic range as an R390A. Seems closer with your testing.

If possible, I'd like to see your testing a representative modern rx as a comparison instead of just relying on Sherwood's measurements.

Also, I looked around your web site...very nice construction projects...you do excellent work!

73,
Dan
W1DAN

Well Done.. :) I'm in good company with my collection .... I thought i picked right...

Thanks for the work...

Dan,
I think Jay will agree, you can take Bob Sherwood's numbers to the bank.

Hi Frank:

I agree that Bob Sherwood's measurements are excellent. I do not doubt them as he has spent years in creating the numbers. I bet W1VD's numbers are also accurate.

I was just thinking about some little setup difference that just might make the numbers between W1VD and Sherwoods a little different.

One big difference I hear between the oldies and SS rigs of today is the shape of the IF passbands. As you know the older rx's have steep curves while today's rigs have flat passbands (except the R390A). To me, the old rx's curved passband causes "that old radio sound".

Dan

Measurements were made in cw bandwidths. All receivers had BW choices at or  close to 500 Hz except the R-390A with choices of .1 and 1 kHz so I split the difference. Blocking and two-tone DR were pretty much identical in the two BW, as expected.

SS-1R writeup ready soon...

Didn't do the 2 kHz tests because the receivers on the 'old' performance list weren't measured at that spacing. Will have a look as time permits. Yes, there was certainly a downturn in performance with the first solid state receivers - a lot like the situation with the first solid state stereo amps.

Agree...have no reason to think Bob Sherwood's measurements aren't good as gold - met him back in the 70s and he's a straight shooter. The real test would be to measure the very same receiver on both test setups. I've seen several dB difference (occasionally  more) between the same model receivers. These differences may be less on newer equipment with fewer alignment adjustments. Also, would put day to day measurement repeatability at about 1 dB. Recently picked up a K3 and when the cw roofing filter arrives that will make for a very interesting test.

Yes, tube receivers seem to have a 'warmer' sound than solid state. <Note: not spoken as an audiophool.>  ;)   

also no two receivers of the same part number perform exactly the same on every frequency.