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HQ-170 Alignment




 
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Author Topic: HQ-170 Alignment  (Read 300957 times)
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n5op
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« on: September 28, 2013, 09:59:31 PM »

I need some advice for my HQ-170. I've realigned it by the book, but it's still not quite right. Specifically, it seems like an IF pass band isn't properly centered. He're's the symptom: when I center the BFO and then switch side bands, I should see symmetric behavior: the frequency I hear from the xtal calibrator in LSB at an S-meter reading of, say, S5 should be the same as what I hear on USB.  So, as I tune across the xtal calibrator signal, I should hear the same range of audio hetrodyne frequencies regardless of which sideband I select, but I don't. Put another way, if I switch to upper sideband and listen to a 2700 Hz tone, I see a much higher S meter reading than when switch to lower sideband and listen to a 2700 Hz tone. One of the IFs isn't properly centered.

Part of my problem may be suboptimal signal generators but I've been as careful as I know how to be. I've read the circuit theory, but it's pretty sparse and I'm not clear about what I need to do differently. This is easy to set on my TS-930S, but this beast is different. Any and all help is appreciated.

73,

Kim N5OP
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WQ9E
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« Reply #1 on: September 28, 2013, 10:29:25 PM »

Kim,

You do need to use an accurately calibrated signal generator for the 60 Khz. IF alignment and also make sure the BFO is properly set to zero beat this generator frequency with the BFO set to center.  As I recall there are some differing alignment instructions in different versions of the HQ-170 manual but I always do the 60 Khz. IF alignment with the selectivity set to .5 and the sideband set to USB as called for in the HC-10 manual.

With the Hammarlund system both the IF bandwidth and passband frequency passed are switched as you change selectivity and sideband.  I have a feeling that most of the HQ-170/180 (and HC-10/SPC-10) straight from the factory would not have provided perfectly equal sideband response at all bandwidth settings and this certainly will not improve with component aging.  Although I like my Hammarlund receivers I much prefer the same era Hallicrafters system where only the bandwidth was changed in the IF channel and sideband selection was via conversion crystal switching (either 50 Khz. above or below the prior IF frequency).  With the Hallicrafters system properly aligned you can tune an AM signal to zero beat and select either sideband and the audio will sound the same but none of my Hammarlund receivers will do this at all bandwidths although most are fairly close.  If one sideband is seriously muffled when aligned and tuned properly then you will have to take a look at the capacitors and resistors used in the bandwidth and sideband selection system.  But before doing this make sure that the alignment is correct and you are tuned perfectly to the signal.  Heathkit used a similar system to Hallicrafters with their RX-1 receiver and they sent out a note providing additional advice since it turned out many users weren't very good at properly tuning an AM signal on a receiver designed to receive one sideband at a time.  Until you get used to it the best way to tune AM is to start with the BFO on and tune the receiver for zero beat.  With a HQ-170 this should result in pretty similar sounding sidebands although not perfect like the Halli system.
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Rodger WQ9E
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« Reply #2 on: September 29, 2013, 02:00:18 AM »

+1 For what Rodger said.   What is required is a stable, accurate signal generator.

Many wouldn't think that these old receivers would require very accurate signal sources, but they really do.   Like Rodger, I too prefer the Hallicrafters design approach because its simpler and the response is inherently symmetrical.

My HQ-180 had differing response on the two sidebands as well,  and with its narrower band width wasn't particularly well suited to AM, so I sold it and bought an NC-300.   
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Mike KE0ZU

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n5op
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« Reply #3 on: September 29, 2013, 10:29:04 AM »

Thanks to you both! With all it's flaws, I probably won't sell it as I have a strong emotional attachment to it-- I simply need to learn how best to align it. I too have found different alignment methods, all in Hammarlund's own documents!

In my case, the documentation says to align it at 0.5 kHz and LSB, but I'll try it with USB to see. As I understand it, the 60 kHz IF is the last IF (either third or second, depending on the band) and where all detection and selectivity takes place. L4 controls the 395 kHz mixer oscillator that converts from 455 kHz to 60 kHz, so I might be able to do some IF shift tricks. This may take a bit of experimentation...

Kim N5OP
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« Reply #4 on: September 29, 2013, 12:27:40 PM »

For tough conditions the HQ-170 does quite well and I used one with my most used AM station (Ranger driving Desk KW) for quite awhile.  When I first set up this station I used a HRO-50 like the Johnson advertising but I found that the combination of QRM and weak signals were too much for the HRO when I was acting as net control for a vintage 75 meter AM net and the HQ-170 was a big improvement.  From there I used a SX-115 for awhile and now a SX-88 does duty in this position.  But used for its purpose (high performance vintage receiver) it will fill its role magnificently.

The Hallicrafters 5 Khz. selectivity position provides the same general fidelity as a typical receiver with a 10 Khz. bandpass and the audio is quite good in this position.  The HQ-170 either in its single or DSB position provides a maximum effective bandpass equivalent to a 6 Khz. traditional receiver which sounds pretty tight.  With AM you cannot offset tune very far without having insufficient carrier for low distortion demodulation with these steeper bandpass receivers although you can try using "exalted carrier" (use the local BFO to substitute for the transmitted carrier) while experimenting with your receiver. 

My current favorite Hammarlund setup is a HQ-160 with a HC-10 SSB adapter.   The HQ-160 detector/output stage provides nice quality AM when conditions are good and when necessary the HC-10 accepts the 455 Khz. IF output of the HQ-160 and provides the equivalent of the HQ-170 final mixer, 60 Khz. IF, detector, audio system, and slot filter.  I am keeping an eye out at hamfests for a parts SX-101 series because I want to experiment with a SSB adapter roughly equivalent to the HC-10 using the Halli final IF.  I plan to build in a mixer with a two crystal oscillator allowing 455 Khz. input and selection of either sideband. 

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Rodger WQ9E
n5op
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« Reply #5 on: September 29, 2013, 07:48:05 PM »

I cleaned all the switch contacts with DeOxIt then realigned the 60 kHz IF with a signal that was only 9 Hz high (60.009 kHz) as this was as close as I could set the sig gen. I verified that it stayed at the same frequency throught the 60 kHz alignment. No difference! I guess that's simply the way of the receiver in it's current state. It seems symmetric until I get to the 3 kHz bandwidth, where I'm pretty sure the LSB side is too narrow.

I tried playing with L4 (395 kHz oscillator) and that didn't result in a shift in the 60 kHz pass and buy rather a change in the received frequency. Wrong!

Because Hammarlund is rather sparse on it's theory of operation section, I'll have to ponder the beast a bit before I try to make any further progress. I gave the selectivity and sideband switches a hard look and, well... Replacing the switched components is not for the faint of heart.

Kim N5OP
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WQ9E
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« Reply #6 on: September 29, 2013, 08:17:39 PM »

Kim,

Generally receivers with variable selectivity systems like these are aligned at the narrowest bandwidth but if you plan to primarily use the 3 Khz. bandwidth you might try experimenting with an alignment there instead of at .5 to see how you like the results.  My guess is the gain and shape will be a little worse at .5 but the overall results may be closer to what you want.  This would be a worthwhile experiment before you get into component level substitution.

To avoid completely driving yourself crazy if you are planning to try to do in-depth repair first develop a good understanding of how this system works.  If the problem is mostly at a single setting of the bandwidth and sideband selections then you will be able to narrow it down to a small set of components.  If the problems are widespread then plan on making your response and gain variation measurements stage by stage since the components in the three stages will not have aged equally.

If you do end up with a Hammarlund 170 that provides perfectly symmetrical response across all bandwidths and passbands then you will likely have a very rare beast as it could be the world's only one that works perfectly Smiley
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Rodger WQ9E
n5op
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« Reply #7 on: September 29, 2013, 10:08:53 PM »

Thanks, Rodger!

Funny you should mention aligning it for a particular bandwidth... I began that process but bailed when I found how much I had to change things. I certainly could have gotten it to work pretty much as I want at the 3 kHz selectivity (6 kHz with both sidebands) but not at any of the others. I had to pick my poison, as it were and it seemed that I'd sacrifice a lot of sensitivity at all of the narrower bandwidths if I got it symmetrical at the 3 kHz setting. So, I put it all back in a "by the book" configuration and the began carefully examining how well things matched up between LSB and USB at the different selectivity settings. I found that each wetting was different. All tended to show a too-narrow LSB compared to USB, but they weren't all the same.

Since I've known this particular receiver (not just the model, but this very one) since 1970, I began to recall this I'd noticed this since, well... Forever. This is the way it's always acted.

The methods Hammarlund uses to vary bandwidth and sideband with only LC filters (no crystal filters) is pretty clever, but depends a lot on fixed component values. As others have noted, it's unlikely that it came from the factory symmetrical at all bandwidths, though it may have been better than it is now. I have no burning desire to make it a (temporarily!) perfect HQ-170 at each and every selectivity setting, though I probably could if I didn't have a day job. Such a condition would be ephemeral though, as components aged and drifted. I use it mostly with my Globe Champ 350 for AM, occasionally for classic CW, and it does fine for both as it is.

I can only guess that Hammarlund (or Heath) didn't use crystal filters because they were expensive in their day. This method was cheaper though a bit less flexible and less tolerant of drifting component values.

I launched this effort because the RF alignment was off and learned a lot. And, yes, the RF alignment is now spot on!

Kim N5OP
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n5op
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« Reply #8 on: September 30, 2013, 09:38:43 AM »

for anyone that's interested... This morning, before work, I took the time to play a bit with the HQ-170. Feeding a dummy load with my Orion II, I did some testing of the bandwidth at different selectivity settings. I run the Orion II into a dummy load at low power and the receiver gets whatever gets past the isolation provided by the coax switch.

I start out at S 5 (the alignment benchmark) and define the bandwidth as 1 S unit. Ideally, that's 6 dB, but on this receiver, S5 to S4 is a drop of about 4.25 dB. How did I define this? I fed a measured 40 W into the dummy load, set the HQ-170 RF gain to show S5, and decrease power until it shows S4. It's crude, but all I have.  So, 1 S unit (about -4 dB) defines the bandwidth numbers I show here. Here's what I get:

At 0.5 kHz: LSB 380 Hz, USB 380 Hz, Both 680 Hz
At 1 kHz: LSB 560 Hz, USB 560 Hz, Both 1100 Hz
At 2 kHz: LSB 640 Hz, USB 860 Hz, Both 1290 Hz
At 3 kHz: LSB 600 Hz(!), USB 1320 Hz, Both: 2100 Hz

No wonder it sounds a bit narrow to my ear!

Almost all of the receiver's selectivity is in the 60 kHz IF strip, so that's where I need to focus my attention. When I have the time, I'll realign it with the bandwidth in the 3 kHz position and see what I get. The receiver is plenty sensitive everywhere but 10 m, where sensitivity drops a bit. However, I intend to use it primarily for AM, so if I can enhance it for that mode, I'll decide to be happy.

Kim N5OP
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k7pp
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« Reply #9 on: September 30, 2013, 12:58:25 PM »

Hi Kim;
I've done a bunch of videos showing detailed alignment on the HQ 170-A and 180-A and 129-X.  If you can stay awake thru them,(hi)you might find some info that will help you.  Just go to Youtube and search "K7PP".
The guys suggesting an accurate 60khz source are right on.   The RF, high IF and local oscillator can be done without the 60khz generator and in most cases you can make a simple test to determine if you need to do the low IF alignment.   There is also a video on how to do that available.  This test works for all series using the 60khz low IF and no test equipment necessary.
You might also be advised that the last 11 of these radios I've repaired or aligned have had at least one, sometimes more, bad 6BE6's and at least a couple of bad or noisy 6C4's.  
Also,  if T28 is not adjusted right on,  the balance between upper and lower sideband may be off.  This sounds like where you might have an issue.  In the plain 170, the BFO adjustment is available in SSB mode and upper/lower sideband balance can be adjusted right from the front panel but in the 170-A the BFO cannot be adjusted from the front in SSB mode.  Slightly adjusting T28 while in SSB mode and switching between upper and lower will allow you to balance between the two modes.  It may also be an indicator that your low IF needs to be adjusted.  
BTW,  you will find much passionate disagreement on how to do this receiver alignment and mostly due to the fact that there are several versions of the manual and, oddly enough, the first being the most accurate and informative in my opinion.  Some will tell you that the latest manual is the only way to go but,
I'll leave it up to you to decide....I currently have three 170-A's, a 180-A and 129-X and really love the Hammarlund line.

Very Best,
Pete, K7PP
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n5op
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« Reply #10 on: September 30, 2013, 01:59:53 PM »

Hi Pete,

Yes, I ran across your videos on the 170A. Mine's a straight 170, not the A model. I think my source was as accurate as could reasonably be needed: I have a pretty accurate HP counter that I've compared against others here at work that are regularly calibrated against traceable stndards and it compares very well. When I aligns the 60 kHz IF, my injection frequency was 60.009 kHz. I hope that's close as it's as close as I'm likely to get.

I aligned to other IFs by the book, but probably could have down as well using the internal xtal calibrator. T28 adjusts the BFO for zero beat whne the BFO is ceneterd and that's set pretty well. I've treid adjusting the BFO but that doesn't solve my problem. Your videos are good but a bot more comprhensive than i need. I need some specific advice about the 60 kHz IF on the 170. Would it be better to discuss the in-the-weeds details off line?

Kim N5OP
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k7pp
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« Reply #11 on: September 30, 2013, 02:15:19 PM »

Sure, Kim;
I'm new to the board so I'm not sure if I can IM or not.
I am good in QRZ.  Pete
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n5op
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« Reply #12 on: September 30, 2013, 03:26:52 PM »

Hmmm... Me neither. Well, then, my e-mail is
cw underscore de underscore n5op at sbcglobal dot net.

Let's get set up that way. Once I figure this part out (with your help), I'll document what I had to do and post it here for archival.

Kim N5OP
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Pete, WA2CWA
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« Reply #13 on: September 30, 2013, 04:16:12 PM »

The no reason not to discuss the intimate details here. Others may learn from the discussion. We generally don't bite.
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k7pp
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« Reply #14 on: September 30, 2013, 05:57:34 PM »

OK,  Thanks,  Pete.
Don't wan't to make any nubie mistakes if at all possible.

Kim;
I'll drop you an e mail when I get home but in the meantime,  any chance you
could take a peek at this video and let me know how your receiver responds?

I didn't say so in the video but you are looking for an S meter increase to tell you if alignment is needed.
The rest is self explanatory and by no means the best way to test but it gives
you an idea of what the receiver might need.

Best,  Pete

https://www.youtube.com/watch?v=4l1hWNvPe2g
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n5op
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« Reply #15 on: September 30, 2013, 10:52:41 PM »

Hi Pete,

Nicely done!  I did the test with mine and I see that as I change bandwidths on either sideband, I see no changes, but I do see a change between LSB and USB. USB S-meter readings are uniformly lower that LSB S-meter readings. On 0.5 kHz, the difference is zero, at 1.0 kHz, the difference is 1.5 S units, at 2 Khz, the difference is 2.5 S units and at 3.0 kHz the difference is 3 s units (all starting at S 6).

So, I fail the "equality of sideband selection" test. I have what I believe is the original HQ-170 manual and followed the alignment procedure in it. What's next? As an aside, i tested the tubes in the receiver and all tested good with my Weston tube tester. I know that tube testers really test mainly emission and transconductance and so don't tell the whole story. I have spare NOS tubes, but I don't thingk that's where my problem lies based on the test you outlined.

As I said earlier, I aligned it with an injected signal of 60.009 kHz (9 Hz high). Is that accurate enough? That's about as close as I can get with the equipment I have. I don't have a 60 kHz crystal for a crystal oscillator source, though I wish I did!

Kim N5OP
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k7pp
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« Reply #16 on: October 01, 2013, 12:41:41 AM »

Kim,  
Please bear with me a bit on this and perhaps consider trying a simple adjustment which might help me understand if it is alignment or component.

Turn your SSB selector to "Both".

Turn your mode selector to AM.

Turn on your crystal calibrator and find a signal you can peak for maximum.

Adjust your RF gain for an S7 reading on your meter.  (don't want a saturating signal)

Adjust your BFO KHZ position to zero.   (even though your BFO is off)

Switch your "select khz" switch to .5 or narrowest position.

Now switch your "sidebands" switch back and fourth between upper and lower while adjusting the frequency knob until you find a spot where there is no change in the S meter reading.  It will be critical and it may take you a bit of
playing to get it.

When you find that spot,  turn on your BFO and adjust T 28 for a Zero beat.

This will put your filters in a position to provide equal sideband detection on either side of the received signal.

This is the easiest way I can think of to determine if it's adjustment vs component failure.

It just may be that your BFO and 60khz IF's and Product detector are not
lined up....

When all this is done,  try the aformentioned test again and see how you do.
If the S meter change goes up when you switch from .5 to 3 khz bandwidth, you may still have a misaligned 60 khz IF or a component failure.
As you may have noted in the video,  I could change from .5 to 3 khz and from upper to lower to both without an S meter change.   If you can make that happen,  you're dead on.
If this test procedure works for you I can toss together another video doing it on my own equipment or if you are more comfortable having the video already done so you can reference it,  just give me a day or two to get my film crew, director and studios set up....Hi.

Good luck
Please let me know.

Best,   Pete



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n5op
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« Reply #17 on: October 01, 2013, 10:25:58 AM »

Easy enough, Pete! I'll have to haul it back to the workshop, but it's not a big deal. Especially since I work at a Federal lab -- though I'm not a Federal employee -- I should have time on my hands for the foreseeable future.

Kim N5OP
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k7pp
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« Reply #18 on: October 01, 2013, 01:22:09 PM »

OK,  Kim;
In the meantime,  I'll get busy with another one of epic videos. 
I should have it posted this evening.

I cringe at the thought of folks doing a capacitor change out or some other major repair on one of these receivers when it just might be a simple adjustment.
My next video will show all four of my receivers hopefully acting the same way during the test I mentioned.
Sometimes it's a matter of being able recognize "normal", so you have a baseline.

Pete
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n5op
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« Reply #19 on: October 01, 2013, 04:56:23 PM »

Ha! You don't as much as I do when I consider actually doing such a thing!

Kim N5OP
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k7pp
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« Reply #20 on: October 01, 2013, 06:46:14 PM »

OK,  Kim;
Hot out of the film room.  My latest "B" movie.

I did a comparison between four Hammarlund receivers and the results can be
viewed at:

http://www.youtube.com/watch?v=DD-kIXIUX-s


Good Luck;
Pete, K7PP

aka:   Cecil B. DePete
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n5op
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« Reply #21 on: October 03, 2013, 04:57:49 PM »

Well, I followed the procedure for adjusting T28 and I still have the seam problem: the LSB is much narrower than the USB. Any additional ideas, or is it time to 1) decide that this is just fine or 2) disassemble the selectivity switch stack and start replacing components?

Kim N5OP
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k7pp
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« Reply #22 on: October 03, 2013, 09:24:26 PM »

OK,  Kim;
If your willing....

Switch on the Cal and find a Cal signal on any freq you chose.
Switch to .5 bandwidth and then switch to upper sideband. 
peak the signal on the S meter.   
Adjust the RF gain control for mid scale.
Take note of the reading.

Now switch to lower sideband and tune the receiver back and fourth for maximum S meter reading.   Take note of the reading.
Question:   Can you duplicate the S meter reading if you retune the receiver while in lower sideband or is the  reading "low" in the lower siband position no matter what you do?  I think you can see where this test is going.

I'm trying to ascertain if you have a leaky cap or perhaps a bad switch section.

All of the filtering for upper and lower sideband are done in the lower IF (60kz). The switching of different values of caps change the upper and lower sideband selection.  Your symptoms could include a bad wafer section or a leaky cap.
It would help to know these things in order to know where to start trouble shooting.
Also,  you mention that the lower sideband seems to be narrower?   

Regards,
Pete
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n5op
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« Reply #23 on: October 03, 2013, 10:15:52 PM »

Thanks Pete! Yes, the LSB is narrower on the 2 and 3 kHz settings. I'm an amateur musician (violin), and I'm fortunate to have very good relative pitch. -- I can recreate a given tone over a short period with very high accuracy. Zero-beating the BFO as in the first test, I find that the bandwidth of the 0.5 and 1 kHz settings are about the same (same tone yields same S-meter reading in each sideband), but there's a *big* difference at 2 and 3 kHz -- at higher pitches the same tone yields vastly different S-meter readings, and -- before anyone asks -- yes, I'm on the proper side of the signal.

Here are the results of your suggested test. My standard was S7:

Selectivity    LSB     USB
     0.5         6.9      7.0
     1.0         6.0      7.0
     2.0         5.8      7.0
     3.0         5.8      7.0

There's an asymmetry in the IF chain and the culprit appears to be in the LSB position. Next hint?

Kim N5OP
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k7pp
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« Reply #24 on: October 04, 2013, 11:49:34 AM »

Kim,  let me do one more last video.  You may be describing a normal condition but what you are seeing is a bit confusing to me.   I sure don't want to see you tearing into your radio if it's an alignment issue.   Give me a day or so. 

Best, Pete
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