Question HQ-180 performance in 15-30MHz band.
 

Got a nice HQ-180 off of ebay. Works great except that the sensitivity
seems
off in the top band 15-30 MHz. Tried aligning it and I can either peak it up
at the low end or the high end but not both. Seems the tracking of the 2nd
RF
filter (the one after the RF amp) is off.

Is this normal ? If not any suggestions?

Bill
VE3JHU

Bill, that kind of performance is not normal for the HQ-180. How is
the dial calibration on the 15-30 MHz band? Is the calibration good,
but the sensitivity bad? If the local oscillator is off frequency,
sensitivity will be poor and the calibration will be off. If it is
just a sensitivity problem, then look at the RF stage. My HQ-180 dial
calibration is very good on all bands. You should expect sensitivity
and calibration accuracy on the "top band" to be as good as on the
others.

Best Regards,

Ed

Ed Engelken wrote:
Bill, that kind of performance is not normal for the HQ-180. How is
the dial calibration on the 15-30 MHz band? Is the calibration good,
but the sensitivity bad? If the local oscillator is off frequency,
sensitivity will be poor and the calibration will be off. If it is
just a sensitivity problem, then look at the RF stage. My HQ-180 dial
calibration is very good on all bands. You should expect sensitivity
and calibration accuracy on the "top band" to be as good as on the
others.

Best Regards,

Ed

Yeah but......If he's listening in the evening lately, the bands are pretty
dead up there. Might that be mistaken for a 'lack of sensitivity'?
Just asking.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html

Thanks for the replies so far.

I am testing with a HP lab quality signal generator so it is not band
conditions.
Frequency calibration seems quite reasonable acroos all the bands.

Found a couple of things today:
In the RF amp circuit,
R2 was only 100 ohms instead of 1K.
C7 at the non V+ side of R2 was not connected to ground.
- Fixed these but didn't seem to make much of a difference

Found that grease from the bearings of the main tuning capacitor had
gotten onto the rotor contacts at the front. I noticed this because when I
jiggle the main tuning knob by accident, the signal level jumped.

I think the mixer and following circuitry is working ok.
Removed the RF input lead to the mixer and directly injected the signal
from my signal generator. With a source of 50 ohms the S meter read S5
across the top 3 bands. When I injected the signal through a 1 K resistor
the signal level dropped as a function of frequency.

I will continue to focuss on the circuitry around the RF amp and possibly
cleaning up the switch contacts. I tried swapping tubes but that made no
difference.


Nice radio though.

Bill, VE3JHU





"Ed Engelken" wrote in message
oups.com...
Bill, that kind of performance is not normal for the HQ-180. How is
the dial calibration on the 15-30 MHz band? Is the calibration good,
but the sensitivity bad? If the local oscillator is off frequency,
sensitivity will be poor and the calibration will be off. If it is
just a sensitivity problem, then look at the RF stage. My HQ-180 dial
calibration is very good on all bands. You should expect sensitivity
and calibration accuracy on the "top band" to be as good as on the
others.

Best Regards,

Ed

Does the antenna trimmer work properly? That is, do you get a sharp
peak in the response when it is adjusted? If the antenna trimmer works
across the band, then the antenna coil is OK. My HQ-180 had a broken
wire in the cable coming from the trimmer cap.

Best Regards,

Ed

The antenna trimmer works fine. The first stage of RF filtering works well
across
all the bands. The antenna trimmer obviously helps here as it is just a cap
in parallel
with the tuning cap. My problems seem to be coming from either the RF
after, or the
following tuned circuits/switches.

Did have a damaged primary coil on one of the input transformers though,
T16. It was fried.
I wound 2 turns and this fixed it.

Bill
"Ed Engelken" wrote in message
oups.com...
Does the antenna trimmer work properly? That is, do you get a sharp
peak in the response when it is adjusted? If the antenna trimmer works
across the band, then the antenna coil is OK. My HQ-180 had a broken
wire in the cable coming from the trimmer cap.

Best Regards,

Ed