[VHFcontesting] [NEWSVHF] 222 activity night

Fri Oct 25 09:11:36 EDT 2024

I am pretty sure that all of those other Larcan amps are working 
reasonably well.  The one that went to Good Buddy Ron had a hex put on 
it in an attempt to cancel the hex that GB Ron put on me and K3SK. I 
learned that trick from a Jamaican girl friend last year. I met her in a 
bar in Berwick. She was driving taxi.

I would add that you should never buy an MRF151G from China. They are 
all made out of Chinesium and will not work.  Most likely relabeled 
junk. Only buy it from a reputable source here in the US of A.  I have a 
FM TX that has 2 X MRF151Gs in it. I was going to put it on 144, but 
decided to save it for the FETs.   I am working on two more amplifiers 
here. One is  a 1000 watt unit and the other is a 1500 watt unit for 
KF0M.  I am adding filtering and VSWR protection circuits. That is one 
of my winter projects.

I am wondering if the problem is a parasitic oscillation that 
intermittently appears. The 500 watt amp has a similar bias bypass as 
the 1500 watt amp. I believe it is a .01 chip. Possibly adding a .001 in 
addition might be a good idea. Maybe a chip on the drain rail as well. I 
am just guessing here.

Dave K1WHS

On 10/24/2024 12:03 PM, Ron Klimas WZ1V wrote:
> Thanks to all who replied.
> If anyone else got a self-igniting amp like mine from Good Buddy Dave,
> Here's the link to the correct schematic so you can repair it:
>
> https://www.mmra.org/larcan/15kWhidocs.pdf
>
> Replacement non-exploding chip caps are available from Mouser,
> the values on the output network of each FET are -
> 30 pF in parallel with 27 pF, 39 pF x2, and 6.8 pF,
> example Kyocera 800B270JT500XT for the 27 pf.
>
> https://www.mouser.com/c/passive-components/capacitors/ceramic-capacitors/mlccs-multilayer-ceramic-capacitors/multilayer-ceramic-capacitors-mlcc-smd-smt/?capacitance=27%20pF&voltage%20rating%20dc=500%20VDC
>
> There is no reason these caps should have shorted and burned up.
> I suspect I was just unlucky and got a Larcan lemon.
> Just a heads up on the FET's - they are all not created equal,
> SRF3943-2 was the original part, beware of Chinese fake knock-offs.
>
> 73 Ron WZ1V
>
> ----- Original Message -----
> From: David Olean <k1whs at metrocast.net>
> To: newsvhf at mailman.qth.net, vhfcontesting at contesting.com,        "222 >> 222Activity at groups.io" <222Activity at groups.io>
> Date: Wed, 23 Oct 2024 15:05:51 -0400
> Subject: Re: [NEWSVHF] 222 activity night
>
>> Wow, Ron that is quite a list and I see a new call or two there, which
> is great. It is funny how the power level works. When I went from 170
> watts on 2M to 1500 watts I was sure that my grid totals would soar
> during the contest. They did not. All I saw was an increase in the # of
> contacts made. That sure surprised me. 120 watts will still do a lot of
> work!! I worked 15 of the 20 stations that you worked. I missed N2SLO,
> WB2ONA, K and W1GHZ.  Other stations worked here include N1GYT, WA1LWC,
> K3SK and two others for the same total of 20 QSOs.
>
> The excitement of the evening was working WA3EOQ on CW. We set up a sked
> and I saw a big blip just off frequency and about 20 dB out of the
> noise. I tuned it in and it was Howard calling me on CW. I gave him a
> 559 and he passed along a 569. I never missed a dit, and that was the
> strongest I have ever heard him on a Tuesday night.  Knowing that things
> might be up a bit down the coast, I tried FT8 with K3SK. He decoded me,
> and I could tell he was there, but did not decode him.  Normally we
> hardly ever makea contact on FT8. We switched to Q65B-30 and worked
> quickly. -22 here and I was -20 there as I recall.  By about 00:50the
> East Coast was quiet so I quit and listened on 28 MHz for a few minutes.
> Between about 01:15 and 01:30 I could work JAs and VKs on FT8. I saw no
> CW activity. Imagine JAs coming in so late in the evening. The SSB HF
> contest will be Bedlam I am sure.
>
> I was really having fun hearing actual QRM early in the evening. There
> were QSOs on top of QSOs. In short it was a huge amount of fun. Why
> can't a VHF contest provide the same excitement?   That is an
> interesting question.
>
> 73
>
> Dave K1WHS
>
> On 10/22/2024 9:00 PM, Ron Klimas WZ1V wrote:
>
>> Limped along at 120 Watts on 222 tonight, but logged:
>> WB2VVV FN41, WA2LTM FN20, K1PXE FN31, WA3NUF FN20,
>> WB2ONA FN20, K1WHS FN43, N2SLO FN30, AA2SD FM29,
>> KC1DWH FN31, W1AIM FN34, W1GHZ FN34, N1SV FN42,
>> WA3EOQ FM09, WA3SSG FN20, K2RMX FN20, WA1RKS FN32,
>> WA1MBA FN51, WB2RVX FM29, and K3TUF FN10.
>> Anyone know where I can find a schematic and or parts list
>> for a Larcan High Band VHF 500 Watt driver amp ?
>> Having tough time repairing by guesswork.
>>
>> 73 Ron WZ1V
>>
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