I'm starting a separate thread on this in case anyone else has an HQ-170/180 (A/X) they would like to use as a sideband convertor with a 455kC signal from another radio.
I think by looking at the schematics, there is an HC-10/SPC-10 hiding in every 170/180.

Here are the schematics/manuals.

SPC-10
http://www.hammarlund.org/PDF/SPC-10.pdf

HC-10
http://gmcotton.com/Ham_Radio/MISC%20Ma ... Manual.pdf

HQ-180AX
http://www.hammarlund.org/files/HQ_180AX_SCHEMATIC.pdf

My first guess at where to tap into on the 180AX schematic would be the junction of T4 and L2/R24/R25.
However, on the 180AX schematic there is an extra transformer (T5) between L2 and the convertor that isn't there on the HC-10/SPC-10 schematics.

Am I at a good starting point here, or should the tap go after T5, or have it go through T3, 4, and 5, or even sooner? Am I even close at thinking it should go somewhere between V2and V5 on the 180AX schematic?

Edit : Looking through the 180AX manual alignment instructions, it says it should begin to pass a 455kC signal at pin7 of V2. Possibly start the 455kC input tap here?

So far I think it's at the junction of T5 and C28 , T4 and L2/R24/R25 , or pin7 of V2

I'd start with the junction of L2 and T4 if you want the slot control to work. Break the connection to T4. Connect the input to L2.

Tony

I turned a parts HQ-170 into a SPC-10 for my SP-600. But for someone looking to build a sideband adapter from another radio I really think the Hallicrafters SX-96 (and descendants) system is better. You would need to add an additional mixer stage to convert your radio IF (i.e. 455) to the Hallicrafters 1650 input. But from there you get electronic sideband switching that doesn't depend upon switching response curves in the selectivity stages. The Hallicrafters system will always demodulate only one AM sideband but in its 5 Khz. position it provides response out to 5 Khz. (equivalent to 10 Khz normal AM detector) as opposed to the maximum 3 Khz. bandwidth for the HC-10. In the 6 Khz. position the HC-10 is set up for DSB so each sideband is still cut starting at 3 Khz.

When some other projects are wrapped up I will start watching for a SX-100 (has notch filter) or later Halli selectable sideband receiver. A Heathkit RX-1 uses the same system but with a slightly different first IF.

Rodger WQ9E

Sounds good but at the moment I don't have any Hallicrafters with sideband capability, but have two Hammarlunds (a 180A, and a 180AX with silencer). The one with the silencer has less problems than the other one and has a couple mods to the chassis and case, so I'm really not against modding it some more. Was just looking for a way to more or less switch out the internal 455kC from the 180AX to a 455kC from another receiver, as a "can it be made to function like an SPC-10?" project/idea.

Switchable back and forth (or both for diversity??).

In another post about the 180AX, I suggested maybe something as easy as making a set up of some sort to just run the IF out from an external receiver to one of the crystal sockets on the 180AX ( no diversity this way due to an internal relay that switches out the VFO to use the crystals instead). Sounds too easy. Way too easy to be without difficulty.

@ Tony, and other blackbelts in radio circuitry. What's the effects of tapping into different points on the circuit? I noticed the capacitance is different going to the 180AX V5 (because of the transformer in between it and L2?). Would there be any up or down side to taking the external 455KC and running through the 180AX 455KC amplifier (would it need it with that transformer in the mix?), or 455KC gate, or even farther back??

@ rsingl. Where did you inject the external 455KC signal at in your SPC-10 from a HQ-170 project?

Well, I think I have a few belts to go to get to the level of some of these other guys but I'm always willing to take a shot at it. The cap you are referring to is different because of the impedance of the circuit. The IF transformer is not there in the HC-10 (probably to reduce cost and save space on a crowded chassis) so the slot circuit is connected directly to the mixer. This is a lower impedance circuit so you need a bigger cap. With the transformer in there, it appears that the impedance is higher so the small cap works fine. The input impedance of the slot circuit looks to be pretty low in both cases so I am guessing that you can just hook it up like I said as a first try. If worse comes to worse, you might end up modifying the whole thing to get that slot circuit to look exactly like the one in the HC-10 but I'm guessing that won't be necessary.

Tony

Rodger,

With the passband tuning of the HQ-180, you should be able to tune it so that the entire 6 khz of the filter is being used on one sideband of the AM signal, right?

Tony

Tony,

In theory you should be able to but I have never had success with my HQ-170 or 180 in this department. The passband tuning for these receivers is really a vernier tuning control (which is how Hammarlund labeled it on most of the HQ-170 receiver production). I think maybe there is enough ripple in the "both" position at 6KC that it just doesn't sound good. For a really good passband tuning implementation, try a Drake R-4C with good quality filters, on CW it is fantastic.

Properly tuned I have really good luck with the Halli selectable sideband receivers.

Rodger WQ9E

Ok, anyone care to take a stab at what kind of attenuation or cap I would need to tap in @ Where Tony suggested?
The signal for now will be coming from an R-390A. I suppose different tap points/transformers call for different attenuation.
My best guess is the least amount of attenuation from the 390 with the least amount of amplification from the 180?

It will be going through at least that 1 transformer before L2 though.

I'd read somewhere else that I could just stick a 455KC crystal in one of the 180AX slots, and run the 390 IF out to the antenna input of the 180AX, but that's putting the whole radio in the mix when it doesn't have to be, BUT, requires no mods.

Hmmmmm.

Not sure what you are asking. Just take the output of the 390a, run it through a .01 or .05 or .1 cap from your junkbox directly to L2 where it connects to T4, after disconnecting T4 from L2. It isn't going to damage anything. The worst that can happen is that it works poorly. The cap is just a safety precaution in case you hook it up wrong. It doesn't need to go through any other transformer before it gets to L2. If the performance is not up to par, then you can dig into the signal levels and such.


Tony

@ Tony. Was curious if the 455kC signal from the 390 would need to be taken down to an acceptable level as to not put too much signal to L2.

No worries Mike. The HC-10 has a very wide input range, .005 to 2 volts. My R-390a is putting out about .030 volts on the IF out. Should be fine, even accounting for the differences in the input network. If anything, there won't be enough signal, but I doubt it.

Tony