HQ-145 sensitivity
 

Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after adjusting
the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc on
that band setting. I wonder if this was a design compromise? Or is there
still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!

Tnx,
Joe K9LY

HQ-145 sensitivity
 

In article ,
"Joe L." wrote:

Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after adjusting
the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc on
that band setting. I wonder if this was a design compromise? Or is there
still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!

Tnx,
Joe K9LY

Worse here on a working 145A. WWV 20-40db over 9 on the 4-10 range.
S3-S5 on the 10-30 range. Seems more sensitive at 30Mc than 10Mc here
too. However, I can't vouch for the alignment that a friend did 6 years
ago for me.

Please keep us posted.

Best,
Mike KM6WB

HQ-145 sensitivity
 

This is typical of many receivers. It is generally caused by variations
in local oscillator injection to the mixer. As you change the amount of
capacitance with the tuning capacitor, you change the amount of feedback
in the oscillator. Most oscillator circuits suffer from this.

73,
Darrell, WA5VGO



Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after
adjusting the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc
on that band setting. I wonder if this was a design compromise? Or is
there still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would
please check whether theirs operates the same way. Just tune into WWV
at 10 Mc on both band settings and see if there's much difference in
signal strength. Thanks!

Tnx,
Joe K9LY

HQ-145 sensitivity
 

On Apr 22, 3:05*pm, Darrell wrote:
This is typical of many receivers. It is generally caused by variations
in local oscillator injection to the mixer. As you change the amount of
capacitance with the tuning capacitor, you change the amount of feedback
in the oscillator. Most oscillator circuits suffer from this.

73,
Darrell, WA5VGO

Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after
adjusting the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc
on that band setting. I wonder if this was a design compromise? Or is
there still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would
please check whether theirs operates the same way. Just tune into WWV
at 10 Mc on both band settings and see if there's much difference in
signal strength. Thanks!

Tnx,
Joe K9LY

You are correct about the injection, but the HQ-145 did not suffer
from this, at least mine did not. Check the Oscillator injection -
you will probably find that it is down due to a bad component. Either
the tube is weak or you have a bad bypass cap. Also check the values
of all of the resistors with a meter.

Tim AA6DQ

HQ-145 sensitivity
 

On Apr 22, 1:40*pm, Mike wrote:
In article ,
*"Joe L." wrote:





Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after adjusting
the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc on
that band setting. I wonder if this was a design compromise? Or is there
still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!

Tnx,
Joe K9LY

Worse here on a working 145A. WWV 20-40db over 9 on the 4-10 range.
S3-S5 on the 10-30 range. Seems more sensitive at *30Mc than 10Mc here
too. However, I can't vouch for the alignment that a friend did 6 years
ago for me.

Please keep us posted.

Best,
Mike KM6WB- Hide quoted text -

- Show quoted text -

My restored and aligned HQ-160 shows the same sort of difference on
the two bands. IIRC, the oscillator injection was similar on both
bands. Sounds like this is a generic problem with Hammarlunds of this
vintage.

Neil S.

HQ-145 sensitivity
 

Great answers, everyone. Thank you very much for all the input. I will
probably spend more time on it this weekend, and will report my findings
here.

Tnx & 73,
Joe K9LY


In article
,
nesesu wrote:


My restored and aligned HQ-160 shows the same sort of difference on
the two bands. IIRC, the oscillator injection was similar on both
bands. Sounds like this is a generic problem with Hammarlunds of this
vintage.

HQ-145 sensitivity
 

Hi Joe. My HQ-145 exhibits a very slight difference between the 10 Mcs
sensitivity on the 4-10 vs 10-30 Mcs bands. I spent a lot of time reworking
it last year and am very pleased with the result. Remember that the 10-30
band is double conversion an you should pay a lot of attention to the
adjustment of the 3035 Kc circuit. I ended up replacing T5 in mine because
someone had tried to repair the original and flowed some solder on the
bottom coil.

73 & Gud Luck!
K3PID
Ron H
--
This outgoing email was scanned by
Norton Antivirus Corp. Edition
and found to be virus free!

HQ-145 sensitivity
 

"Joe L." wrote in news:invalid-
:

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!



Joe, does the receiver hear the atmospheric noise in its most insensitive
spot? As long as the receiver can hear the natural noise level around it,
what difference does it make if it's sensitivity is 10uv or .01uv? The
answer is NONE. With all the racket on HF, a super-sensitive receiver is a
CURSE, not a feature. All the new radios are way too sensitive for HF with
their stupid S-meters showing S more than 1 with no signals. You end up
listening to racket and riding the AGC level control.

It's crazy....

--
-----
Larry
You can tell there's very intelligent life in the Universe
because none of them have ever tried to contact us.....

HQ-145 sensitivity
 

On Apr 22, 1:00*pm, "Joe L." wrote:
Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after adjusting
the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc on
that band setting. I wonder if this was a design compromise? Or is there
still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!

Tnx,
Joe K9LY

I had one of these a while back. The first thing I noticed about the
HQ-145 is the lack of real electronic components within a huge
cabinet. There is plenty of real estate there! Some of the circuits
are pretty much bare bones and this includes the conversion/
oscillators. When the second conversion oscillator "Kicks In" it makes
up for the overall gain that was lacking on the lower band which was
single conversion. The HQ-180/160 didn't P-600 so I suspect they were
the top design and all the others just had stuff taken out to cut the
overall cost of the receiver. This radio was one step up from the
single conversion HQ-100 which suffered from image rejection problems
fixed by the double conversion of the HQ-145. I think the double
conversion setup was minimal and could have been more well thought out
to balance the gain a bit better.


Tony

HQ-145 sensitivity
 

On Apr 22, 1:00*pm, "Joe L." wrote:
Hello. I've been restoring a Hammarlund HQ-145 that has been neglected
for many years. After performing the RF alignment, I noticed that the
sensitivity at 10 Mc on the 10-30 Mc range is about 10 dB worse than
when tuned to 10 Mc on the 4-10 Mc range. This was even after adjusting
the 10-30 Mc ANT and RF coils as instructed by the manual.

The sensitivity is actually much better at 30 Mc than it is at 10 Mc on
that band setting. I wonder if this was a design compromise? Or is there
still something flaky with my HQ-145?

I would appreciate it if someone else with a working HQ-145 would please
check whether theirs operates the same way. Just tune into WWV at 10 Mc
on both band settings and see if there's much difference in signal
strength. Thanks!

Tnx,
Joe K9LY

I had one of these a while back. The first thing I noticed about the
HQ-145 is the lack of real electronic components within a huge
cabinet. There is plenty of real estate there! Some of the circuits
are pretty much bare bones and this includes the conversion/
oscillators. When the second conversion oscillator "Kicks In" it makes
up for the overall gain that was lacking on the lower band which was
single conversion. The HQ-180/160 didn't P-600 so I suspect they were
the top design and all the others just had stuff taken out to cut the
overall cost of the receiver. This radio was one step up from the
single conversion HQ-100 which suffered from image rejection problems
fixed by the double conversion of the HQ-145. I think the double
conversion setup was minimal and could have been more well thought out
to balance the gain a bit better.


Tony

HQ-145 sensitivity
 

In article ,
Larry wrote:

Joe, does the receiver hear the atmospheric noise in its most insensitive
spot? As long as the receiver can hear the natural noise level around it,
what difference does it make if it's sensitivity is 10uv or .01uv? The
answer is NONE. With all the racket on HF, a super-sensitive receiver is a
CURSE, not a feature. All the new radios are way too sensitive for HF with
their stupid S-meters showing S more than 1 with no signals. You end up
listening to racket and riding the AGC level control.

It's crazy....

Larry,

No, it definitely can't hear the atmospheric noise in its most
insensitive spot. So I'm pretty sure the gain is lower than it should be
at that spot on the dial. Otherwise, you're right... there's no point in
having a super-sensitive receiver when the atmospheric noise is what
limits your noise floor.

Tnx,
Joe K9LY

HQ-145 sensitivity
 

Finally got back to the HQ-145 project. Borrowed a 100 MHz oscilloscope
to measure the 1st LO injection level at V2-1.
Band: 4-10 Mc, tuned to 10 Mc: 20 Vpp (LO freq = 10.455 Mc)
Band: 10-30 Mc, tuned to 10 Mc: 0.9 Vpp (LO freq = 13.035 Mc)
That's a big difference!

Measured at several freqs in the 10-30 Mc range:
10 Mc 0.9 Vpp
11 Mc 3.3 Vpp
12 Mc 4.7 Vpp
13 Mc 6.1 Vpp
15 Mc 8.3 Vpp
20 Mc 13.0 Vpp
25 Mc 14.4 Vpp
30 Mc 13.7 Vpp

So, clearly the 1st LO amplitude is very low at the bottom of the 10-30
Mc range. The 1st mixer 6BE6 seems to need at least 5 Vpp of LO in order
for the receiver to have decent sensitivity. I suspect the LO coil tap
point is less than optimal for the low-freq end of the band as the
result of some sort of design compromise. (Better-quality receivers like
the HQ-180 divide the HF band coverage into smaller ranges so the RF and
LO circuits can be more optimized.)

I also happen to have an HQ-100 which is very similar to the HQ-145
except it is single conversion throughout. The difference in sensitivity
at 10 Mc on the two band settings was much smaller than on the HQ-145,
but still noticeable. I pulled the 6C4 tube from the HQ-100 and tried it
in the HQ-145, but the LO wouldn't even oscillate unless tuned to 13 Mc
or higher! That was odd.

I couldn't measure the LO level in the HQ-100 because oscillation would
cease whenever the oscilloscope probe was touched to the 1st mixer. LO
is pulled from the grid of the 6C4 in the HQ-100, whereas it's pulled
from the cathode of the 6C4 in the HQ-145. This might be why the scope
probe kills the LO in the HQ-100. Other than the pull-off point, the LO
circuit appears to be the same for the two receivers.

Well, this has been an interesting exercise. I don't think I'll do
anything further about the HQ-145 except maybe try to get a N.O.S. 6C4
and see if it makes any difference on the 10-30 Mc range.

73,
Joe K9LY


In article ,
Darrell wrote:

This is typical of many receivers. It is generally caused by variations
in local oscillator injection to the mixer. As you change the amount of
capacitance with the tuning capacitor, you change the amount of feedback
in the oscillator. Most oscillator circuits suffer from this.

73,
Darrell, WA5VGO