Garey Barrell <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- Gerry -
As I said, the R-4B is excellent for _communications quality_ AM. It is quite suitable for listening to AM communications in crowded band conditions. You don't _have to_ use exalted carrier for AM, but you DO need to adjust the PB tuning for one sideband rather than centering it.
The thing that "saves" the R-4B for AM is the gentle slope of the L-C filters. It results in a smooth rolloff of highs giving a "soft" sound. A 4.8 kHz crystal filter with a 2:1 shape factor would sound very muddy on an AM signal.
The SP-600 would be a good choice for AM. Most all the "big box" receivers were designed with AM in mind up until you get to the HQ-170, NC-303, SX-101, 75A-3 era. Then even the IF strips were getting narrow even before the filters were added.
It need to be a sturdy table for the SP-600 and Viking II !!
I like my NC-300 for AM. Or the HQ-129X.
73, Garey - K4OAH
Gerry wrote:
It's excellent on AM without any changes whatsoever. You don't need to use exalted carrier reception to receive AM on the R-4B. Just how good it is will depend on your personal tastes. I bought one back in '70 which I later sold and bought another one about 10 years ago which I still have. The 4.8kHz passband is good for general AM listening. Any wider than that and you'll pick up a lot more noise. Any less and signals will sound excessively muddy. The thing to keep in mind is that the R-4B selectivity comes from its 50kHz IF stage. In other words, transformers with selectable coupling to achieve several degrees of selectivity. This is a kind of L/C filter with gently sloping stopband characteristics as opposed to crystal or mechanical filters with steep skirts. It would be more accurate to say the R-4B has selectivity "steps" rather than filters. If you're looking for wider passband then consider something else. A good one is the Hammarlund SP-600, for example. It might help to balance the weight on the other side of the table from your Viking II.
n7ioh <[EMAIL PROTECTED]> made an utterence to the drakelist gang
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Hi, I am currently trying to decide if the R-4B would be good for AM reception in the ham bands. I would like to use the radio with my Johnson Viking Ranger II. I am currently leaning toward the R-4B because of cost and all the good things I have heard and read about it. I was told that the R-4B filters may be to narrow for really good AM? Others have said that this is not true and that the R-4B would make a fine receiver for AM. Anyone use this receiver for AM and are there any mods that I should or could do to improve the AM? I like everything about the R-4B just have concerns about using it for AM. I will also use the radio for SSB and some light CW use so I don't want to degrade the radio in these areas. Thanks in advance for your help and input.
Al N7IOH
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