No r.f. generator and 50kcs alignment.............

[RolandSWL]

Hi All,

I have a few radios which have 50kcs I.F chains. Not wanting to leave well enough alone, I'd like to explore aligning these units.
I don't have an r.f. signal generator that goes down to to 50kcs, only 100kcs. Is there another way to do the alignment?

Thanks and stay safe, Roland.

[n4joy]

Hi, Roland.  I did a quick search and found this discussion related to your question on the Antique Radio Forums: https://antiqueradios.com/forums/viewtopic.php?f=8&t=316425   Good suggestions there.

Just curious, why do you feel that they need aligning? 

Chris, N4JOY

[WQ9E]

I used a HP audio oscillator before I acquired a signal generator that handled 50 Khz. IF alignment.  Many of the older audio frequency generators go up to 100 Khz. or more, I used a classic HP that uses a night light bulb as the negative resistance element.

Depending upon which set you are aligning, you may have to align the final IF at a slightly different frequency.  For example, the Hallicrafters sets with a ~50 Khz. IF are very common and proper final IF alignment is very dependent upon the frequencies of the two conversion oscillator crystals used in the final mixer.  If one or both of those crystals have drifted slightly, then you have to make a slight change in the final IF frequency to compensate.

Rodger WQ9E

[KW4H]

Hi All,

I have a few radios which have 50kcs I.F chains. Not wanting to leave well enough alone, I'd like to explore aligning these units.
I don't have an r.f. signal generator that goes down to to 50kcs, only 100kcs. Is there another way to do the alignment?

Thanks and stay safe, Roland.

Consider a TinySA.  It does many things, but is a cheap ($59) and highly accurate signal generator that will easily do 50 KHz.  You can pump out an unmodulated or modulated signal.  Drawback is that you can't (at least for now) set the signal level in microvolts -- but you can reduce it by various db.  The TinySA isn't my main signal generator, but gets used a lot.  A couple of hints on the TinySA:  1) don't buy if off of Amazon -- there are many fakes.  A good source is R&L Electronics.  2) Always use a DC block and external attenuators.  

I have found the TinySA to be an invaluable part of my toolset -- it's like Felix the Cat's magic bag, only about the size of a cell phone.  You can check oscillator frequencies in a flash by attaching the external whip antenna and waving it near the oscillator tuning cap.  

The official specs on it say the output range is 100 KHz to 350 MHz.  That's actually not true -- see the photo for proof.  I've run my TinySA down to very low frequencies and had no difficulty whatsoever.  And verified to be accurate against a frequency counter.  The 100 KHz bottom end is only a specification, not a limit.  

More information:  https://www.tinysa.org

Steve, KW4H

[RolandSWL]

Thankyou for your replies. Do they need alignment? I won't know until I verify. I have lots of test equipment that I rescued before it went into a landfill. It's truly heartbreaking how much perfectly good stuff my company has discarded over the years. Anyway, I do have a TinySA. The only drawback is that it has ancient firmware and as such, is not very easy to use. I have a very nice LEADER audio generator and a frequency counter. How do I interface the audio generator with the radio? How big a signal do I use?
Thanks........

[KW4H]

Thankyou for your replies. Do they need alignment? I won't know until I verify. I have lots of test equipment that I rescued before it went into a landfill. It's truly heartbreaking how much perfectly good stuff my company has discarded over the years. Anyway, I do have a TinySA. The only drawback is that it has ancient firmware and as such, is not very easy to use. I have a very nice LEADER audio generator and a frequency counter. How do I interface the audio generator with the radio? How big a signal do I use?
Thanks........

Normally, the only real specification for signal levels is to not overload the target because you want to find a sharp and solid peak.  I usually adjust the output level to something reasonable but obviously not overkill.  As far as tying the signal into the IF goes, it depends on the design of the radio.  Typically, in the case of tube radios, you insert the IF signal into the grid of a convenient and appropriate tube, using a capacitor if need be.  The IF chain in radio starts somewhere -- you want to inject your signal ahead of the first IF transformer but you also want to be careful of any B+ and manage that accordingly.

Understand about the TinySA.  You can update the firmware; however, it does indeed have a small screen.  I've found mine to be indispensable and worth the effort to deal with because I have limited workbench space (pulling out the SG-85 can be an ordeal); however, anything that can accurately generate that 50 KHz signal you need is A-OK.  Just make sure you validate it with a frequency counter and watch for drift.

Steve, KW4H

[KD6VXI]

One of the inexpensive VNAs that have hit the market would work as well.


--Shane
WP2ASS / ex KD6VXI