Problem with fundamental

[NS5K]

New member with what I think is a strange problem- first had two xtals;
thought they were bad.

 I got 2 new crystals (7010 & 3890) fand have the same problem in three
different radios:

Drake 2-NT
Hallicrafters HT-40
And Heath DX-60B

The problem is

80 meters - 5 watts
40     "      - 8/9 watts
20     "      - 25/28 watts
15     "      - 40 (HT) to 55 watts
10     "      - 30  "   to  70 on Drake and 58 on the DX

Same problem as before with 3 radios and there is nothing to tune
and as  a retired commercial radio tech with 35 years exp. find it almost
impossible to have 3 radios with the same problem. the real odd part is
the plate current is what it should be but with low output.
The above readings were with a bird 43 calibrated  with my 100 watt slug.

Anyone have any thoughts? I have another HT on the way and I have
a strange feeling it will be the same- something external?  Also used several
coax cables.

Thanks Larry

[KA0HCP]

Did you order the crystals as new manufacture?  What specification?

Perhaps they are the wrong spec for these radios....

[NS5K]

Thanks for your response
I ordered from Brian Carling, AF4K and he says they are usable
in the listed radios- hard to buy same problem with 3 radios.
I had to repair both the DX and HT

May just use the alc limit circuit in my ic-7600

Thanks
Larry

[KM1H]

If these are FT-243's open and see what is inside; he is well known for soldering in miniature crystals which in your case are possibly overtone typs.

Carl

[NS5K]

Thanks Carl; I believe you are correct as I think they
are hc-49's inside- don't know about being O/T-

I do know this: I have emailed him four times and HE does
not answer me yet.
Does anyone know of another vendor for real ft-243's not
what I believe are re-manufactured.  I just could not find
another vendor.

One more thing that will really confuse is I have a HG-10B
and it does the same thing??

Larry

[WQ9E]

Larry,

Very strange, are you using a dummy load for your measurements?  Try different coax?  What does your modern transceiver show for output on 80?  With three radios showing the same symptoms I would start to question the test setup.

The crystal style should work OK in the rigs you listed but not in some of the bigger and older gear which has far too much current through the miniature crystals hidden in the FT-243 case.  Since the VFO has the same behavior I doubt if the crystals are the problem.

[W7SOE]

It is rare to find an overtone xtal below 30MHz...

[NS5K]

Rodger

I am using dummy load and have swapped out coax jumpers even used my
THP watt meter and all the same- my 7600 does 100 watts and drive my amp to
700 pep- on AM with 25 in I get about 160-165 watts carrier but very easy
for the alc to limit it to abt 60-70% mod; after that you get downward mod.

Yes I agree but as a tech I find it very hard to comprehend 3 radios doing exactly
the same- even tried at 3 am on 3890 and I am getting 1.5 watts- all the above
were just in the cw mode. and all three have new oscillator tubes- even checked
surrounding caps in osc circuit- but am getting frustrated because the is nothing to tune, even went to a different room in the house to eliminate the ac power!

IN my experience its going to something very simple that I am overlooking.

Thanks
Larry

I am new to the board and really thank all for your quick input

[WQ9E]

Larry,

For the HT-40 and DX-60 how does the loading control affect the output (I realize the 2NT has fixed loading components)?   Low output with normal plate current sounds a lot like excessive loading reducing efficiency.  With the DX-60B can you reach the rated 2.5 mils of grid drive?

[NS5K]

Rodger
 
Not sure what you mean about loading but grid easily gets to 2.5ma
I double check to see that I only had one plate dip and the loading
has only one point where max power occurs- I thought very early that
maybe I had a self oscillation problem but I can see on my 7600 scope
that it is on freq and I think self osc. would manifest itself without a
crystal-

I like your input but have been working on this for weeks- if I find the
problem history shows it will be something stupid-
I bought an HT-40 mark 1 this week and I hate to think what I might do
because he sent me a picture with 3885 crystal on cw with about 45
watts- abt right for 75 input I think.

Larry

[WQ9E]

Larry,

On the DX-60B on 80 meters start with 2.5 mils of grid drive and with the load control close to zero (loading capacitor should be fully meshed) and then increase loading in small amounts while dipping the plate current with the plate tune control.

[NS5K]

OK Rodger - in the I'll do that in the am- have all
disconnected right now.
Larry

[KM1H]

It is rare to find an overtone xtal below 30MHz...

Not true.

It is also easy to find someone selling an overtone at its fundemental and not telling the customer. However I doubt it in this case since its 80M that is the problem.....my mistake.

[KA2DZT]

New member with what I think is a strange problem- first had two xtals;
thought they were bad.

 I got 2 new crystals (7010 & 3890) fand have the same problem in three
different radios:

Drake 2-NT
Hallicrafters HT-40
And Heath DX-60B

The problem is

80 meters - 5 watts
40     "      - 8/9 watts
20     "      - 25/28 watts
15     "      - 40 (HT) to 55 watts
10     "      - 30  "   to  70 on Drake and 58 on the DX

Same problem as before with 3 radios and there is nothing to tune
and as  a retired commercial radio tech with 35 years exp. find it almost
impossible to have 3 radios with the same problem. the real odd part is
the plate current is what it should be but with low output.
The above readings were with a bird 43 calibrated  with my 100 watt slug.

Anyone have any thoughts? I have another HT on the way and I have
a strange feeling it will be the same- something external?  Also used several
coax cables.

Thanks Larry

I would look for an open in your test set-up.  Seems that there is a connection that is not making full contact.  The capacitance between the parts of a connection will pass the higher freq signals more than the lower freqs.

Hope this helps, or at least gives you some direction with this problem.

Fred

[KA3EKH]

I don’t know, I have been using his crystals for some time now with the only issue being that in some feedback circuits they will fail unlike the real FT-243 crystals but they are cheap and fast, also I have had one or two that were off frequency but he did get back to me and replace them at no cost including shipping. I am currently using couple of his crystals in my RCA BTA-1MX on 1.885 in an 807 oscillator and its holding up well and have several other tube radios on 40 and 80 and they work. If you have plate voltage and current and are seeing a resonate dip would assume you're making power somewhere, are you using a HF slug on the bird? I know from experience that the VHF slugs read way wrong at HF even the low band slugs. I had to buy a stupid expensive 3 to 30 slug for mine to work correctly. You may want to try the light bulb thing where you get a 40, 60 and 100 watt light bulb and use them. They make surprisingly good loads at low frequency and give a visual indication of output power.
Ray F.

[NS5K]

Rodger and all

I did the tune-up as Rodger said which is the way the manual
says; result > no difference abt 3 watts out on 80.

Replaced all the tube agn and used DeOxit on the tube sockets.
Have used more than on watt meter; used different jumpers
(coax) and my 7600 shows 100 watts key down and 30 on AM.
I had checked the B+ before and I get higher power (to abt 60)
on the higher bands- I have the HT-40 Mark one coming probably
May second and if I get the same results I will throw in the towel.

Off topic; tell me if I need to start a new one--- but has anyone
heard an ICOM 7600 on AM

73
Larry

[KX5JT]

Frank, WA3JBT has (among many radios) an IC-7600 and I have worked him on AM with it.  It sounds above average for a "ricebox" on AM.  No real problems.  Good communications quality.

Unfortunately you can't hear the IC-7600 tx on this little video but here is his IC-7600 rx on 40 meter AM early in the morning.

http://kx5jt.net/AM/KX5JT-as-seen-from-WA3JBT-5-28-10.MOV

[Jim, W5JO]

Do you have a frequency counter?  If so, what does it read when you are tuned?

[NS5K]

KX5JT thanks for that-- could you tell me the set-up as
I see is all positive modulation.
W5JO- no freq counter but can see on 7600 scope and on freq.
That does not mean I am not looking at a spur- that"s where a
spectrum analyzer would help as the 7600 will go to +/- 250K.

Larry
NS5K

[NS5K]

KX5JT sorry misread your post- do you know how WA3JBT
has his 7600 set-up?

Larry

[Jim, W5JO]

W5JO- no freq counter but can see on 7600 scope and on freq.
That does not mean I am not looking at a spur- that"s where a
spectrum analyzer would help as the 7600 will go to +/- 250K.

You may see an on freq. blip, but if the majority of the power is elsewhere you may be tuning on a multiple of the fundamental.  Are there other hams near you?  If so maybe one of them has an MFJ 259B and it has a frequency counter in it.   Using a freq. counter with a scope probe will help find out where things are wrong.