We don't need no stinkin' sweep generator....

Discussion in '"Boat Anchor" & Classic Equipment' started by KD6RF, Jan 12, 2011.

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  1. KD6RF

    KD6RF Premium Subscriber QRZ Page

    ...or any signal generator for that matter in order to align the IF section, including the notorious crystal filter and phasing circuits. It takes about a half hour once you get used to it, perhaps an hour or so the first time.
    Having recently acquired a few Hammarlunds, I found that they mostly worked, but that the filter/phasing alignment was wayyyy off, perhaps due to aging, or more likely, judging by the marks on the alignment screws and cans, due to a previous owner giving up on the alignment of the filter section.

    So, here is the alignment procedure I came up with for aligning the HQ145 and HQ129 - feel free to comment, praise, add to, or bash! The steps are: 1 and 2 - find the IF crystal frequency, step 3 - align the IF, steps 4 and 5 - align the crystal filter/phasing section, step 6 - verify filter center freq and passbands and perform slight re-tweek if necessary.

    1) Tune in a low strength signal - AM radio is probably best. We want a signal that is weak so that we hear the white noise hiss along with the signal.

    2) Turn selectivity control to max. Turn phasing control straight up (plates of phasing cap half way in both stators). No matter how badly the IF and filter circuits are misaligned, you will be able to find the very sharp crystal filter frequency. Carefully tune receiver to show max reading on S-meter.

    (At this point we hear a very muffled AM radio station and have tuned the receiver such that we have nailed down the crystal frequency that the rest of the IF and filter will be aligned to. It turned out to be 455.8 KHz in my case.)

    3) Turn selectivity control off. Align all IF transformers and coils (excluding the crystal filter units) as we normally would - peak them for max S-meter reading. Some peaks are fairly broad - try to center them up.

    (Old timers will probably remember doing this without an S-meter by listening to the signal and tuning the transformers/coils for minimum high frequency sound content. When you have swooshed in the sound of the AM station in this way, you know that all transformers/coils are centered on the IF.)

    4) Turn selectivity control to some low setting - 1 or 2 works well. Now, tune the slug of the second crystal filter section can (second from front panel for the HQ145) or the upper screw (for the HQ129) so that you hear **maximum** high frequency content. It should sound only slightly muffled, with no ringy-ness.

    5) Peak up the slug of the first crystal filter section can (closest to front panel for the HQ145) or the lower screw (for the HQ129) for max S-meter reading.

    6) I noted some interaction between the last two alignments, and to a lesser extent the IF transformers/coils. Switch back to max selectivity and make sure tuning dial is tuned to max S-meter reading. Switch up and down the selectivity switch settings and you should see just what is described in Hammarlund's manuals - you should see that the S-meter shows peak reading at exactly the same setting of the tuning dial. Re-tweek the slug of the second crystal filter section can (for the HQ145) or the upper screw (for the HQ129) if you see any difference in the position of the tuning dial for max S-meter reading among the selectivity settings. Careful, only very slight movements of the slug or screw at this point. A bit of re-tweeking of the IF transformers/coils will give us a nice symmetrical passband for all settings of the selectivity control, including "off".

    That's it.

    Tuning in to a stronger AM station, and tuning around while observing the S-meter, I found that the published Hammarlund curves are spot-on for the two receivers I aligned. Listening to SSB signals, the phasing control now works nicely along the lines of a modern RIT receiver where you can attenuate the crap out of an interfering signal above or below the desired frequency depending upon the phasing control setting. Sweet.

    I find that selectivity settings of 1, 2, or 3 are nice for SSB, settings 4 and 5 are great for CW.

    Hope this helps those who don't have access to signal generators or sweep generators take the plunge.
     
  2. KF6KXG

    KF6KXG Ham Member QRZ Page

    HQ Rcvr Alignment without sweep generator

    Thank you for posting this. It is exactly what I need to align my 129X. I have aligned many Hallicrafters, but this was my first Hammarlund and I was not happy with the job I did. I was waiting until I found a sweep gen to redo it, but your method will eliminate that expense. 73 Mike KF6KXG
     
  3. KL7AJ

    KL7AJ Premium Subscriber QRZ Page

    I've aligned a lot of boat anchors using just a broadcast station as a signal generator.

    The only problem I see with this method is that you have to have the I.F. frequency pretty close if you want to assure you get single signal response from the crystal filter. You can sometimes shift the I.F. out far enough that it's no longer in the passband. (At least on National receivers)

    I am impressed with the selectivity you can get with a single conversion receiver with a good crystal phasing setup. ;)

    Eric
     
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    That's one way of doing the job.

    I like to use another receiver, one that is fairly accurate in reading frequency. I'll use the receiver to sniff out the local oscillator. I'll tune the receiver to that weak BCB station and set the LO on the proper frequency with the second receiver.
    Then it's a simple matter of peaking the IFs.
     
  5. KD6RF

    KD6RF Premium Subscriber QRZ Page

    Good useful info on how to get the IF close. One of the IF transformers in the HQ129 was pretty far out, but the filter crystal frequency was still by far the dominant factor with a very obvious peak on selectivity setting 5. (Interesting to hear that other designs may throw other peaks in the passband response.)

    And it is, of course, the filter crystal's frequency that we must align the filter section to. When we are sitting on the peak of the filter crystal's response then the LO is by defintion on the right frequeny as well, which in my case was 455.8 KHz away from the AM station's freq.



    Another rather obvious note - once we have found the filter's frequency, and are sitting right on top of it with the AM station's carrier, now is the time to adjust the BFO control for zero-beat.



    Great forum ereryone - picked up alot of good info here, and hope to contribute some as well. Next on the stack - the Gonset GSB100. Warc bands maybe? :)
     
  6. KM1H

    KM1H Ham Member QRZ Page

    Ive never used a sweeper on those old 455 IF Hammarlunds and have been pushing the by the ear procedure for decades on other forums. It doesnt take many runs at it to get very good.

    Your procedure is also very similar to the one in the RME 45 manual.

    The major problem Ive found in the WW2 Super Pros and the HQ-120/129/140X is that crystal activity is sometimes low and it has to be removed and cleaned. Its a chore compared to the ease of a vintage National or Halli.

    Having a good stable SG is no longer an expensive task and sure makes alignment, tracking, and sensitivity measurements simple. Then its just as easy to use it for the filter but for those in poverty the ear has always done well.

    Carl
     
  7. KA4DQJ

    KA4DQJ Ham Member QRZ Page

    Sounds like a plan to me! I got by without a signal generator for years, and finally bought one. Surprise!... I was so used to the "caveman" method of alignment that I still preferred to use a broadcast signal and/or a second receiver. It was easier than figuring out how to use the generator.

    Two types of radio techs... school-trained, and outhouse-trained. Guess I'm the latter.
     
  8. KM1H

    KM1H Ham Member QRZ Page

    Im the 3rd type. A US Navy trained ET (ET School Great Lakes 1960) where we were taught to think on our feet when the going got tough and the tough got going:D

    Carl
     
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