Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: "Acceptable" drift in Hammarlund HQ-170A?  (Read 3136 times)
K3STX
Member

Posts: 956




Ignore
« on: February 16, 2010, 08:02:05 PM »

I know the gripe about this RX is that it is drifty; tonight after 1 hr warm-up I measured about 1 kc/hr drift (from hours 1 and 2 after warm-up). After about 2 hr warm-up I measured 0.25 kc/hr.

How is this? Should I replace the 6C4 oscillator tube (I just bought three), or is this about as good as I can expect?

paul
Logged
N2EY
Member

Posts: 3833




Ignore
« Reply #1 on: February 17, 2010, 12:12:51 AM »

On which band?

250 Hz per hour on 40 from a receiver of that vintage is pretty good. Remember that the higher you go in frequency, the higher the LO is.

73 de Jim, N2EY
Logged
W8JI
Member

Posts: 9304


WWW

Ignore
« Reply #2 on: February 17, 2010, 03:27:29 AM »

I know the gripe about this RX is that it is drifty; tonight after 1 hr warm-up I measured about 1 kc/hr drift (from hours 1 and 2 after warm-up). After about 2 hr warm-up I measured 0.25 kc/hr.

How is this? Should I replace the 6C4 oscillator tube (I just bought three), or is this about as good as I can expect?

paul

It sounds about like my HQ-180 and HQ-170 if you are talking 40 meters or 20 meters.

It also will have "chirp" or warble from AGC pulling the fine tuning oscillator as AGC voltage changes.

Thats the beauty of old radios. They are less than perfect.
Logged
K3STX
Member

Posts: 956




Ignore
« Reply #3 on: February 17, 2010, 03:57:09 AM »

Oops, yes, I meant on 40 meters.

So this tube is OK. Maybe not great. I will try the other two tubes I just got to try to find the "best" one, as I have read that tube-to-tube can change this drift. And I have not noticed the chirp yet. I always run the AF gain at max and use the RF gain as a volume control, so maybe that is why?

I just finished putting a (new) clock in it with the old Hammarlund face, sweet!

paul
Logged
W8JI
Member

Posts: 9304


WWW

Ignore
« Reply #4 on: February 17, 2010, 06:29:52 AM »

Oops, yes, I meant on 40 meters.

So this tube is OK. Maybe not great. I will try the other two tubes I just got to try to find the "best" one, as I have read that tube-to-tube can change this drift. And I have not noticed the chirp yet. I always run the AF gain at max and use the RF gain as a volume control, so maybe that is why?

I just finished putting a (new) clock in it with the old Hammarlund face, sweet!

paul

Unless the tube is actually defective, say a very low emission that gradually builds up or perhaps gassey with emission variation over time, the tube will not affect drift. The primary sources of drift are inductors and capacitors changing value with heat, and mechanical movement causing changes in resonant frequency of the oscillators.

The AVC/AGC induced "chirp" only occurs when the AGC is fully functioning and on strong signals.


Logged
K9LJH
Member

Posts: 58




Ignore
« Reply #5 on: February 17, 2010, 08:40:17 AM »

I had a HQ 1- something or other in the very early sixties with my original license.  As far as I was concerned it was a drifty POS that gave new meaning to the term "chasing DX".  The only gear I miss from those days are my bug and my d-104

But hey, if you think that is a charming and endearing characteristic, then by all means, enjoy it.

This time I am starting off by refurbing a Drake CLine. And that is not to say that me, INRAD and Sherwood Eng won't be spending some time together.

LeeH
KC9RFL
Logged
K3STX
Member

Posts: 956




Ignore
« Reply #6 on: February 17, 2010, 09:04:06 AM »

I thought I read somewhere that some 6C4s were better than other 6C4s for the drift, must be thinking of something else.

I have not replaced a SINGLE anything in this RX, everything is original, so perhaps I don't notice any chirp because the AGC is not working well. I DO know that I nearly blew my head off when I mistakenly didn't turn the RF gain down enough when I was using the RX as a "sidetone monitor", so maybe it does need some work. But since I am using a DX-20 as my TX I am not scouring the bands looking for weak signals anyway.

paul
Logged
N2EY
Member

Posts: 3833




Ignore
« Reply #7 on: February 17, 2010, 09:35:42 AM »

K3STX: "I thought I read somewhere that some 6C4s were better than other 6C4s for the drift"

There may be a slight difference; it depends on the situation. No harm in trying all of the 6C4s you've got; if nothing else, it will tell you if any of them are bad.

But there's no point in buying more in the hope that one of them will magically eliminate the drift, because in a receiver like the '170 it's due to a whole bunch of things.

K3STX: "since I am using a DX-20 as my TX I am not scouring the bands looking for weak signals anyway."

Why not? You'd be surprised what can be worked with a decent antenna when conditions are good.

Since the first of the year I've been spending a lot of time down on the low end of 80 CW, in the evenings. Without really trying I've snagged MD0, GI0, UR8, E77, ZS1, and a couple others I can't recall offhand. The rig I used is the one shown on QRZ.com; the antenna is a homebrew inverted V with traps for 40 meters. Center at about 40 feet, ends maybe 12-15 feet, on a small suburban lot. Of course some of those DX stations have pretty big setups, but they all came back to me and gave good reports.

Your DX-20 is only about 5 dB down from my 100 watter.

73 de Jim, N2EY
Logged
G3RZP
Member

Posts: 4328




Ignore
« Reply #8 on: February 17, 2010, 10:47:47 AM »

As I recall, the HQ170A, if switched off with the RF Gain control and the AC left connected,  kept the 6BE6 and 6C4 heaters alight to reduce drift. Are you switching off at the wall by any chance?

The drift figures don't sound excessive. Makes me wonder how we worked SSB on 10m with them, though.....It is 40 years since I used one in anger, though.
Logged
K3STX
Member

Posts: 956




Ignore
« Reply #9 on: February 17, 2010, 10:55:27 AM »

Yes, the heaters are alight all the time. I should make sure I remember to unplug it if I go out of town for a while, however. Actually, since I really only use it on the weekends for QSOs I should probably unplug is normally.

And yes, Jim, I probably could work that good DX on 40CW or 80CW with my antennas, that is as long as they are listening on 3527, 7028, or 7055 kc! I can do it with my QRP rig, why not the DX-20!

paul
Logged
W6OU
Member

Posts: 184




Ignore
« Reply #10 on: February 17, 2010, 11:04:03 AM »

In the HQ-170A the filaments of the first converter and hf oscillator are always energized as long as the receiver is plugged into 120 VAC power and regardless of whether the receiver power switch is on or off. Was your line cord unplugged for a long time before you conducted your drift test? If so, try a retest after the line cord has been plugged in for several hours. The receiver will still drift but perhaps not as much.

The only reason I swap 6C4 tubes is when the oscillator activity starts to die near the edge of the 10 meter band.
Logged
K8OT
Member

Posts: 22




Ignore
« Reply #11 on: February 24, 2010, 07:24:26 PM »

I haven't done it for a long time but you can check the caps in the Osc curcuit and see if they are silver mica or NPO type npo's have different Temp coeficent
it's been a long time but you can change them with the same capitance but a different NPO number depending on which way they drift.
Those old rigs left the filements on the Osc, but when the rest heat up they add some more heat to the Osc curcuit.
Hope this helps. excuse my poor schpelling LOL .... ..
ED K8OT

PS as I remember the clock was there to turn the rig on an hour or so before you operated.
Logged
N4UE
Member

Posts: 289




Ignore
« Reply #12 on: February 28, 2010, 10:53:23 AM »

Hi Paul. I have a 170A also. It 'was' pretty much a drifter as yours. I did a complete recap (see my review here on eHam). That helped, but then I did what I do with all my boatanchor reaeivers.... Add a small muffin fan.
You can do this easily, and not drill holes, etc. I just use some double-sided tape to stick the fan where it will circulate the air best. I had a local PC repair shop save all the NFG PC power supplies. The 12 VDC fans used in the ps are 'usually' OK.
Make up a simple bridge / cap and tap into the heater of a nearby tube. Runnung the fans at <12 VDC makes them completely inaudable. I use them in my Collins right down to my Lafayettes.....
Just keeping a small airflow help those old parts age a wee bit more gracefully. ha ha
The fans make a HUGE difference in my Drake TR-6 (19 tube room heater)....

ron
N4UE
Logged
SWL377
Member

Posts: 108


WWW

Ignore
« Reply #13 on: March 05, 2010, 11:16:02 AM »

My 170 and 180 drift about the same as your 170 so unless you want to make some mods, this is about as good as it gets with these old Hammarlunds in stock condition. I really like them. Quiet, sensitive and reasonably stable for a non synth non PTO rcvr.

You can fool around with neg temp coeff caps and such, but in my experience controlling temperature around the oscillator sections produces the best results in BA rcvrs.

I'll take the 170 and 180 the way they are. Bumping the tunning once in a while to stay on freq isnt a big deal. They drift, but not so much that it is a big problem.

You wanna see drift on higher frqs? My Hallicrafters S 40 can drift circles around your BA rcvr. It isnt even drift, I call it spectrum wandering. On higher freqs my Halli takes tuning dial settings as suggestions not commands.

73
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!