AM Receiver IF filter

[N4LTA]

That is what I have heard and expected. The phase shifts seem to be worst with the mechanical filters according to some old timers who say that Collins ruined SSBs reputation with them.  I have not had any experience with them.

I do remember the juke box sound from the old console AM radios as a child.

I thought it was great.

Pat
N4LTA

[KM1H]

Thats why many consider the pre SP-600 Super Pros the best sounding of the boatanchors.  With continuously variable IF selectivity out to 16 kc and triode connected 6F6 driver and PP audio it sure sounds nice. The down side is the continuous drift.

The Collins R-390 has all LC selectivity but IMO its nightmarish mechanicals are a turn-off to many.
I sure do like listening to my Zenith 12S265 and RCA 811K consoles.

Carl
KM1H

[N2DTS]

What would be the audable effect of the phaze shift?
The Scott slrm and Halicrafters SX17 had no filters and push pull audio out, and did sound very nice, but the IF was not sharp. they would go narrow and wide, the Scott even had a 'hifi' position, but off frequency stuff would get through.

Brett
N2DTS

[Steve - WB3HUZ]

Thats why many consider the pre SP-600 Super Pros the best sounding of the boatanchors.  With continuously variable IF selectivity out to 16 kc and triode connected 6F6 driver and PP audio it sure sounds nice. The down side is the continuous drift.

That would be the Super Pro 200s and 400s. The 600 had single-ended audio. Having had all three, the 200 and 400s are far better sounding, best I've ever heard.

[KM1H]

I Did say PRE SP-600........

Carl
KM1H

[steve_qix]

Interesting topic !!!!

I have built 2 receivers using BC1004s as the "foundation".  These are solid state, but the premise is the same.

No doubt, multiple tuned IF cans will sound better than a mechanical filter, but if it were me, I would have a provision to "switch in" a mechanical (or multiple mechanicals of differing bandwidths) for "battle" conditions.

My high fidelity receiver is absolutely fabulous under most conditions, but when the going gets real touch, I have to either fire up the software defined receiver, or turn on the 75A3 (mechanical filters).

If you've ever used an RBB4, it's similar.  There is a "narrow" position which is quite good - all obtained with multiple resonant (IF) stages.

I have found resistive loading to be quite effective for "widening out" an IF strip.  Small relays are very handy for switching resistors in and out.  Also consider using an LDR (light dependent resistor).  These work well at high frequencies, and offer complete isolation - and some of them - a very wide resistance range.  I use them for AGCing the RF amplifiers in one of my home brew (electrically) receivers.

Anyway, some more info for the stack 

[WQ9E]

I have built 2 receivers using BC1004s as the "foundation".  These are solid state, but the premise is the same.

No doubt, multiple tuned IF cans will sound better than a mechanical filter, but if it were me, I would have a provision to "switch in" a mechanical (or multiple mechanicals of differing bandwidths) for "battle" conditions.

My high fidelity receiver is absolutely fabulous under most conditions, but when the going gets real touch, I have to either fire up the software defined receiver, or turn on the 75A3 (mechanical filters).

Another alternative with the Super Pro for battle conditions is to use one of the sideband converters like the Hammarlund HC-10 for battle conditions.  My HC-10 stays hooked to a GPR-90 most of the time but I have also used it with my SP-210X under trying conditions and it works very well.  The HC-10 is basically the "back end" of an HQ-170/180 receiver containing a mixer to mix a 455 Khz. input down to its 60 Kc IF strip along with AGC and product/AM detector.  It provides a choice of fairly sharp L/C derived bandwidths and selectable sideband for both AM and SSB along with a notch filter.  Since it has its own audio amp choosing the detected signal source is accomplished by either turning up the receiver volume control for "straight" audio or turning up the HC-10 for "processed" audio.

If I ever find the matching SSB converter for the GPR-90 the HC-10 will stay permanently hooked to my "new" SP-400; without the HC-10 the GPR-90 is pretty lousy for CW (weak BFO injection and the BFO tends to lock on strong signals).

Rodger WQ9E

[KM1H]

I agree about the RBB as well as the RBC. For late 30's design they are still very capable today.

I worked on them in the Navy, and never had a failure. It was just routine PM's and testing tubes with a TV-7. I have the first run, black RBB and RBC here.

Carl
KM1H

[N4LTA]

The LDRs are a great idea. I have some that are used in guitar tremolo circuits. Should work very well.

Pat
N4LTA