[Heathkit] WTB: Stand alone HF Receiver

Sat Jul 15 14:42:20 EDT 2017

My .02 FWIW would go with an NC303 or NC300. Got one of each and they're keepers !

Ed K.

> On July 15, 2017 at 12:17 PM Rodger Singley <wq9nsc at live.com> wrote:
>
>
> Steve makes a great point that Hallicrafters has a family of selectable sideband receivers that do a wonderful job on AM in addition to CW and SSB. Using selectable sideband on AM allows you to often enjoy interference free AM when the primary source of QRM is either only above or below the frequency of operation thus you choose to demodulate the sideband with the least QRM.
>
> The Hallicrafters selectable sideband receivers, starting with the SX-96, do an excellent job on AM and I prefer the Hallicrafters method (also used by Heathkit for the RX-1/Mohawk) to the Hammarlund method of providing selectable sideband. In the setup used by Hallicrafters upper or lower sideband is chosen by either high or low side injection in the final mixer so that only the bandwidth of the 50 Khz. IF section is changed as you use the various selectivity choices and response on either sideband is identical. Hammarlund changes both the bandwidth and the frequency of their 60 Khz. IF as mode and bandwidth are changed which is a more complex method and it doesn’t produce as clean a result. With the Hallicrafters setup if you tune an AM signal to zero beat then you can switch sideband at will without retuning while the Hammarlund setup generally also requires a tuning touch up.
>
> Note that with Hallicrafters (and the Heathkit RX-1) with age sometimes one or both of the sideband selection conversion oscillator crystals can drift with age and if they do you need to account for this in the alignment of the final IF and the BFO in order to retain the original performance level.
>
> People are often confused by the bandwidth of the Halli (and Heathkit RX-1) selectable sideband receivers when operating AM because from the marked control it appears too narrow. But these receivers ALWAYS receive AM as only one sideband so the 5 Khz. Selectivity choice is equivalent to 10 Khz. selectivity with a traditional AM receiver. Until you become used to proper tuning of these receivers it is easy to mistune on AM but the learning curve is short. To make it easy to ensure proper tuning as you get used to the receiver characteristics tune in the AM signal in SSB mode with the pitch control (BFO) set to zero and tune for exact zero beat. With a properly aligned SX-96 family or RX-1 receiver this is the exact proper tuning point for correct AM operation and from here switch to AM mode (BFO off) and select the sideband with the least interference. Although most SW broadcasting has disappeared the selectable sideband receiver is more robust against selective fading than a traditional AM receiver and using it in exalted carrier mode (tuned to zero beat and run in SSB mode) it does an excellent job when selective fading becomes an issue. Most of these receivers have a t notch filter and this can be used when in exalted carrier mode to notch out the station AM carrier reducing any heterodyne beat that may occur from slight mistuning/BFO offset.
>
> For ham band only coverage I prefer the SX-115 or SX-101 series to the other Halli selectable sideband units and I wish my SX-88 had the same electronic sideband selection as the later family members but it requires a slight tuning adjustment to select the desired AM sideband in its narrower bandwidth settings. The special very high Q IF transformers in the SX-88 provide a better bandpass characteristic than the later family members but I do miss being able to just flip a switch on AM to remove interference from one side or the other.
>
> The HQ-180 and HQ-170 are also excellent receivers and some prefer them over the competing Hallicrafters so there is definitely personal choice involved. The Hammarlund selectivity system does work quite well and although I am now using the proper matching GSB-1 sideband adapter with my TMC GPR-90 receiver the Hammarlund HC-10 I used previously is far more versatile and I prefer its audio characteristics. The HC-10 is basically the final mixer, 60 Khz. IF, detector, and audio system from a HQ-170/HQ-180 and will greatly improve the performance on ALL modes for many midrange vintage receivers with a 455 khz. IF. One of my favorite Hammarlund setups is a HQ-160 with an external HC-10 because this provides very nice wide AM audio when conditions permit while the HC-10 can be brought into play when needed.
>
> Rodger WQ9E
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
>
> From: Steve Sutfin<mailto:stephoto at mind.net>
> Sent: Saturday, July 15, 2017 10:31 AM
> To: Howie WA3MCK<mailto:wa3mck at gmail.com>
> Cc: Boatanchor group<mailto:boatanchors at mailman.qth.net>; QRP-L Mailing List<mailto:qrp-l at mailman.qth.net>; Glowbug Tetrode<mailto:tetrode at googlegroups.com>; Heathkit<mailto:heathkit at mailman.qth.net>
> Subject: Re: [Heathkit] WTB: Stand alone HF Receiver
>
> The Hallicrafters SX-115 has always been popular or even the smaller
> SX-117.
> 72/73,
> Steve k7dna
>
> On Jul 14, 2017, at 2:49 PM, Howie WA3MCK wrote:
>
>
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