HQ-140X Alignment Question

[nq5t]

I'm pulling a newly acquired HQ-140X out of the cabinet this weekend to do the usual checks, renovation and alignment. 

Question 1.  The 140 manual (like the HQ-120 and all of its subsequent brethren), suggests a sweep generator for IF alignment.  So is there a way to do this without a sweeper?  Will just peaking the IF slugs at the IF frequency (matched to the crystal in the crystal filter) cause bad things to happen?  Is it really worth worrying about, e.g., doing bandpass adjustment manually with just a tunable generator and output meter? yada yada.

Question 2.  The bandspread and main tuning dials have index marks, suggesting that the dials should be set up with the index marks aligned with the dial fiduciaries at the low end of the tuning range when the tuning caps are up against the stops.  Neither of the dials is positioned such that this is the case (just a little off -- maybe 1/4" or less in linear measure looking at the dial), and there's no reference to mechanical dial alignment in the manual.  It doesn't look straightforward to change this setting in any case, although I haven't studied the mechanics thoroughly yet.  Any thoughts on this?

Thanks ... Grant/NQ5T

[Jim, W5JO]

Grant, you can do it without a sweep gen and have a good receiver.  Just put a scope on the detector and align each stage for max, that should take care of you.  Those 140X receivers sound quite good.

As to question 2, it may be that someone removed the dials and repositioned them for some reason or it could be that heat in the cabinet caused the scales to warp a bit.  That is possible since the dial lights are close to the scales.  Take that cover off of the tuning cap and see where everything is.  If the cap meshes properly and you can set the oscillator properly, I wouldn't worry about the marks.

[KM1H]

The 120 manual includes a non sweep procedure that works well  as does the various older Super Pro manuals.  Ive yet to bother with a sweeper on any of them and the filter performance appears dead on.

Ive often wondered why they got so anal over using a sweeper, maybe they didnt trust hams getting loose in the hardware

Carl
KM1H

[N2DTS]

In receivers that use the IF cans to set the bandwidth, the sweeper can show you what the passband looks like.
Many IF cans can have a wide range of shapes (passband) as you tune them, from a sharp peak to a broader double peak.  On many IF transformers, you have two adjustments, or four if it has adjustable caps along with the slugs. This is in the handbooks...

I always wondered if you could look at the response with a spectrum analyzer and band noise to see the shape.
The sdr-iq would be good for that as it goes VERY low, 100 Hz or something silly like that.

Or you could tune the RX to the TX frequency and pump some white noise into the audio and look at the shape.

I will try the sdr-iq on the scope output of the homebrew and see what I get!


Brett

[N2DTS]

Here are some shots of the homebrew rx IF output.
Band noise, kiwa filters, wide is 5.5Kc, narrow is 4.5 Kc.

[N2DTS]

The 2nd shot (above) shows how good the kiwa filters are. That shot was just noise.

With IF cans, you get all sorts of shapes, peaks, gradual roll off of the passband, etc.

Without being able to see the passband, who knows what shape you get, it can be tilted in one IF trans, tilted the other way in another.

I don't think you can get a very good IF bandwidth response out of IF transformers without a LOT of stages and careful adjustments.

Brett

[w3jn]

Sure you can.  Worked fine in the Super Pro series, the SX-28, every HQ series radio, NC-173, 183, 183D, every HRO, etc....

[N3DRB The Derb]

it seems like the 140X almost always survives the years in tip top condx. I have seen so many of them for sale over the last 20 years in close to factory new shape I've lost count. dozens at least, all of them 9++ condition. Most of he other hammarlunds  I see are in the usual varied state of conditions, but I've almost never seen a HQ-140X that was cosmetically in bad shape. I have no idea why but it's enough of a trend over that time span to make me notice.

[KM1H]

Your right about the 140, never thought about it that way. I have 3 of them and one is a factory rack mount. Except for decades of dust the chassis was uncorroded when cleaned up.

Carl