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 Post subject: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 3:28 am 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 376
Location: Butler, PA
Hi all
I don't have the hex tool or the experience to peak the top and bottom
Slugs so I would like to measure it and see if it is to spec. Can I do this
With a frequency counter? And if so where do I take the measurements?
Thanks

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 4:14 am 
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Joined: Jan Tue 10, 2012 8:39 am
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Better get the tool; they don't cost much.

You can sweep across the IF passband and measure the response. A counter won't help much except to calibrate the sweep generator.


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 7:31 am 
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Joined: Jan Tue 16, 2007 7:02 am
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Location: Lexington, KY USA
There is a copy of the manual here:

https://archive.org/download/HeathkitHW3220MeterSSBTransciever/Heathkit%20HW-32%2020%20Meter%20SSB%20Transciever.pdf

Looks as if this 20m transceiver uses a 2.305MHz IF. There is a crystal filter, so the IF will be determined by that.

You might be able to tell something by using a signal generator. It might be pretty difficult to do much with this set without some test equipment.

No doubt Heath relied on pre-adjusted components to allow getting the radio on the air without any real alignment being required, but now things may have drifted, or failed outright.

Ted


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 2:23 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 376
Location: Butler, PA
Thanks Ted I have a RF Gen should i inject the 2.305 Mhz signal at the antenna and then use a freq counter to read it at the L3 can?

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 3:02 pm 
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Cadmandu wrote:
Thanks Ted I have a RF Gen should i inject the 2.305 Mhz signal at the antenna and then use a freq counter to read it at the L3 can?

The circuits don't change the frequency----if you put in 2.305MHz, that's what you'll get out.

To check the tuning, you have to vary the frequency of the input signal and measure the output---using a scope or RF voltmeter (or maybe the set's AGC signal.

As already stated, it's better to just buy the tool and do the alignment-----OR, if it's working satisfactorily, leave it alone.

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"Even if you don't understand Ohm's Law, you are still required to obey it."


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 4:08 pm 
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Joined: Dec Sat 28, 2019 4:18 pm
Posts: 204
Cadmandu wrote:
Hi all
I don't have the hex tool or the experience to peak the top and bottom
Slugs so I would like to measure it and see if it is to spec. Can I do this
With a frequency counter? And if so where do I take the measurements?
Thanks

No, the problem with using a counter to check alignment is that the IF chain can be mistuned and the counter MAY still detect a signal.

Cadmandu wrote:
Thanks Ted I have a RF Gen should i inject the 2.305 Mhz signal at the antenna and then use a freq counter to read it at the L3 can?

Probably not. The antenna circuits are going to be operating at around 14 MHz, not at the IF frequency of 2.305 MHz. If you are going to inject a 2.305 MHz signal into a working IF chain, the best place is the plate of the receiver mixer feeding the crystal filter, in this case V8B, through a suitable DC blocking capacitor.

If the receiver isn't working, start at the input of the product detector and work backwards toward the antenna. Keep in mind that the receiver portion of the Heathkit schematics are drawn backwards with the RCVR input coming from the right. It's a transceiver with the emphasis on the transmitter circuits.

John


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 4:13 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Maybe this is one of those cases where a grid dipper might be the tool to use? Make sure the dipper is accurately aligned, then sniff the transformer for resonance?


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 6:10 pm 
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Joined: Dec Sat 28, 2019 4:18 pm
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I wouldn't. Not enough frequency accuracy, resolution, stability, or resetability. Plus the IF can would, in this case, would add undesired shielding.

For example, you will not be able to distinguish 2.295 MHz from 2.305 MHz on any grid dipper I have ever seen.


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Mon 17, 2020 6:13 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 9153
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
KX5JSC wrote:
I wouldn't. Not enough frequency accuracy, resolution, stability, or resetability. Plus the IF can would, in this case, would add undesired shielding.

For example, you will not be able to distinguish 2.295 MHz from 2.305 MHz on any grid dipper I have ever seen.


Sounds reasonable.

I was wondering about the person without the necessary equipment, if it would at least let them know if they were in the ballpark ... I've not tried it .... just curious.

cheers


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Tue 18, 2020 2:33 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3616
Location: Lexington, KY USA
You really need at least some equipment.

If you have a frequency counter and a meter, you might build a simple oscillator and RF demodulator that could be used to evaluate the IF transformer.

Why worry about this component in particular? There are lots of parts in this radio that might not be working so well any more.

It would be very educational to try to figure out how to check each comonent without the proper test equipment, but it would not be especially practical in terms of getting the radio to work in a finite amount of time.

Ted


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Tue 18, 2020 6:01 am 
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Joined: Dec Tue 29, 2015 8:23 am
Posts: 282
Location: Australia
Usually Lurking wrote:
It would be very educational to try to figure out how to check each comonent without the proper test equipment, but it would not be especially practical in terms of getting the radio to work in a finite amount of time.

Less 'try to figure out how', more 'modify an established alignment technique pinched from elsewhere' :wink:

Inject 30% modulated IF as mentioned above, measure demodulated audio voltage at speaker output with AC meter/scope/whatever. Tune T3 for max. If you can't tune T3, step through several different frequencies around the IF, measuring & recording the audio output voltage at each. Graphing V vs freq will give the response curve, telling you where it's peaked to.

Usually Lurking wrote:
Why worry about this component in particular? There are lots of parts in this radio that might not be working so well any more.

But yes, ultimately this. Plenty else I'd be measuring in there before worrying about the alignment.


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Tue 18, 2020 3:41 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 376
Location: Butler, PA
L3 has a top and bottom slugs that can be moved. I'm directed to tune a station in at a S3 level and then adjust the top and bottom slugs. The top slug has a small hex how do you get down to the bottom. HK manual does not show a pic of the tool.i have a rf gen and a it-12 plus a dmm and a freq counter

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Tue 18, 2020 3:56 pm 
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Location: Littleton, MA
Cadmandu wrote:
The top slug has a small hex how do you get down to the bottom. HK manual does not show a pic of the tool.

See figure 7 or 8 in this GC Electronics alignment tool page:
http://gcelectronics.com/order/SubCatPD ... 80-387.pdf

The slugs are hex all the way through. The shaft necks down behind the hex driver, so you can push the tool through the hex in the top slug, then rotate it to catch the hex in the bottom slug and insert the tool in the bottom slug. If the slugs are too close together, you'll have to move the top slug up to make clearance between the two slugs for the hex head on the tool.

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Tue 18, 2020 3:59 pm 
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Joined: May Tue 30, 2006 4:46 pm
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Location: Santa Rosa, CA
Bottom slugs can be adjusted with a tool like the yellow one in this photo.

Image

The tool can be passed through the top slug because the shaft is smaller in diameter than the slug.

Rich


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Feb Wed 19, 2020 11:10 am 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 376
Location: Butler, PA
Thanks that is a nice set of tools I will buy a few
I have a hr-10 that has a bnc mounted on the back apron that says IF out
Glen said it was for a panadapter.
I will trace out the circuit later today
Can I hook that output up to a scope with a freq counter
My Tek has a connection on the side for a counter output
Thanks for all your help


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Dan W3DKY
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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Mar Fri 27, 2020 4:19 pm 
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Joined: Jan Sun 06, 2013 2:14 am
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Location: Butler, PA
Please read the attachment and tell me where the three transformers get the 2.305 mhz signal from?
All three transformers are to be tuned to the if
Thanks


Attachments:
HW-32 Transformers.docx [11.96 KiB]
Downloaded 17 times

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Mar Sat 28, 2020 12:47 pm 
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Location: Annapolis, MD
In the receiver section, the IF frequency comes from "mixing" the received signal with the local oscillator.

I just skimmed the manual, and did not see a block diagram---deciphering how this works will require reading the circuit description (which I can't do without more coffee)
My guess is that---for transmit---the 2.305 signal is "up-converted" to the actual transmit frequency. This is the same process used to convert the incoming signal to the IF in a receiver.

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"Even if you don't understand Ohm's Law, you are still required to obey it."


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Mar Sat 28, 2020 2:14 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 376
Location: Butler, PA
Thanks Mark
When you say the received frequency do you mean a freq between 14.2 and 14.35 MHz or between 1.618 and 1.768 the vfo frequency?

What freq is the local osc?
Is it static is it 18.750 the het osc
Thanks for the help.

In an AM receiver the IF is created in a dual var cap why do it differently

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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Mar Sat 28, 2020 7:09 pm 
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The key to all this is that the VFO controls both the receive and transmit tuning.

I cannot find the various frequencies in the user guide, but this is how I think it all works:
Receive:
The LO signal is generated by mixing a crystal oscillator signal with the VFO output. At 14.2MHz, the LO signal is either:
14.2 + 2.35 = 16.55
OR:
14.2 - 2.35 = 11.85
When the LO is mixed with the incoming signal, the 2.35MHz IF signal is generated.

Transmit:
The VFO signal is now mixed with the signal from another crystal oscillator to get the transmit carrier.

Thus, transmit and receive frequencies are controlled by separate crystal oscillators, plus the the shared VFO.

If you know the frequency of those 2 crystals, we can maybe work out the details

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"Even if you don't understand Ohm's Law, you are still required to obey it."


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 Post subject: Re: Reading the IF frequency at T3 can on a HW-32
PostPosted: Mar Sat 28, 2020 8:18 pm 
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This Heathkit of the Month article by Bob Eckweiler:
http://www.w6ze.org/Heathkit/Heathkit_070_HW22.pdf
does a good job of describing the frequency conversion scheme in the HW series and provides block diagrams for transmit and receive.

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