Harris FM 20 K pro and con views

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alleo
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Harris FM 20 K pro and con views

Post by alleo »

Just comments on use of one. I've heard a lot of bad things.But as a free transmitter.That we could afford to operate it .All comment are welcome.

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Jim Sofonia
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Re: Harris FM 20 K pro and con views

Post by Jim Sofonia »

The transmitter is fine, probably last a long time. The cavity design has been proven to work and was carried over into the HT line of transmitters. Trouble is if you do have a problem Gates Air has limited support for the older transmitters. You might get help on a good day if they are not to busy. That aside go for it.

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kkiddkkidd
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Re: Harris FM 20 K pro and con views

Post by kkiddkkidd »

Con: Be sure to keep your ear protection handy if you mis-tune the cavity and then try to turn it on...

Pro: Eventually you get used to them going KABANG until you get the tuning straightened out.

IIRC, the IPA was no winner either.

Actually, accepting the lack of parts support and their advanced age, they weren't bad transmitters in their time but as I have said many, many times, putting money in this sized tube transmitter, of this vintage is, absolute false economy...

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Deep Thought
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Re: Harris FM 20 K pro and con views

Post by Deep Thought »

That "free" transmitter will cost you more over the next 10 years in added electrical use and maintenance than a new solid state would. If your electric rates are a bit high then the payback is even faster.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

W9PXZ
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Re: Harris FM 20 K pro and con views

Post by W9PXZ »

Deep Thought wrote:
Mon Jun 01, 2020 10:56 pm
That "free" transmitter will cost you more over the next 10 years in added electrical use and maintenance than a new solid state would. If your electric rates are a bit high then the payback is even faster.
Right on! A 20kW solid state will cost about $100k in round figures new. Figure a 20 year lifespan as a main and that gives you $5k a year. Now consider tube costs at about $2k/yr and high electric bills, that free transmitter is not a good bargain as a main. Adding it as a backup, OK. But not a 24/7 main.

I retired a Continental 5C to backup status last year with a GatesAir FAX40. Going from spending $2500 every 9-12 months on another crappy rebuilt YC130 tube ($5500 new) and the power factor from .80 (at best) to .98 on the electric bill, it will pay for itself in short order. The power bill has decreased enough that the business manager has to include a discrepancy note in her reports to corporate each month on why such a big variance versus last year.

Add in that fact that most of a tube circuit design criteria is negating the inherent distortion of the tube. You might want that distortion in a guitar amp, but not in your RF. The station that got the FAX40 now has a killer signal in what was formerly the fringes from less distortion in the RF. I have seen this effect in every instance of retiring a tube TX with solid state that I have been involved with. From little class A's to full C's. It is kinda funky though going from nearly 10kV at nearly 4A to 43V at 1040A!
Mike Dinger
Wilmington, NC

alleo
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Re: Harris FM 20 K pro and con views

Post by alleo »

I going to re tune our QEI 10,000 its been running ok at another station . So I'll give it new life at this station with lower power see how long it last.

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kkiddkkidd
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Re: Harris FM 20 K pro and con views

Post by kkiddkkidd »

alleo wrote:
Thu Jun 04, 2020 9:45 am
I going to re tune our QEI 10,000 its been running ok at another station . So I'll give it new life at this station with lower power see how long it last.
Good luck my child... May the 4th be with you.
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kkiddkkidd
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Re: Harris FM 20 K pro and con views

Post by kkiddkkidd »

alleo wrote:
Thu Jun 04, 2020 9:45 am
I going to re tune our QEI 10,000 its been running ok at another station . So I'll give it new life at this station with lower power see how long it last.
How far (frequency wise) are you moving it?
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Kelly
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Re: Harris FM 20 K pro and con views

Post by Kelly »

kkiddkkidd wrote:
Thu Jun 04, 2020 11:02 am
alleo wrote:
Thu Jun 04, 2020 9:45 am
I going to re tune our QEI 10,000 its been running ok at another station . So I'll give it new life at this station with lower power see how long it last.
How far (frequency wise) are you moving it?
"Wait, I have to do something to change frequencies??" This guy was on a different discussion board asking similar questions. They are completely clueless, and shouldn't be allowed anywhere near high voltage.
Skype:kellyalford Twitter: @KellyAlford

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kkiddkkidd
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Re: Harris FM 20 K pro and con views

Post by kkiddkkidd »

Kelly wrote:
Thu Jun 04, 2020 2:24 pm
kkiddkkidd wrote:
Thu Jun 04, 2020 11:02 am
alleo wrote:
Thu Jun 04, 2020 9:45 am
I going to re tune our QEI 10,000 its been running ok at another station . So I'll give it new life at this station with lower power see how long it last.
How far (frequency wise) are you moving it?
"Wait, I have to do something to change frequencies??" This guy was on a different discussion board asking similar questions. They are completely clueless, and shouldn't be allowed anywhere near high voltage.
Sort of like the owner that called me one day and told me that their "secret" CP had been granted (everybody in town knew about it) and that they were moving from 100.? to 103.? and that I needed to be at the TX site the next day to change the VS2.5 to 103.?... I said that I would do it but what did they want to do about the ERI combiner and antenna system? He insisted that the TX was frequency agile...

About 6 weeks and $30k later they were on their new channel. One of the large group owners had paid them a lump sum to move so that a distant co-channel station could upgrade to C3. It was so secret that they didn't bother to ask anyone familiar with the site what it would cost to change freq. About half of their big payday went into the combiner and antenna retune.

Later,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
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ChuckG
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Re: Harris FM 20 K pro and con views

Post by ChuckG »

alleo wrote:
Thu Jun 04, 2020 9:45 am
I going to re tune our QEI 10,000
Run the Gates instead. Retuning that QEI is a nightmare you do not want to unleash.
<><><><><><><><><>
Chuck Gennaro
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alleo
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Re: Harris FM 20 K pro and con views

Post by alleo »

To address one writer I am to re tune a QEI from 102.3 Mhz to 104.9 Mhz. According to Bob Brown its a miner change most of it done with use of a ruler inside the PA cavity .He sent to me 6 page instructions on this and is a phone call away should there be any thing misunderstood .And all this done with the main ac breakers pulled ..............

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Re: Harris FM 20 K pro and con views

Post by NECRAT »

alleo wrote:
Mon Jun 08, 2020 2:27 pm
According to Bob Brown its a miner change most of it done with use of a ruler inside the PA cavity .
That may be, but ChuckG, the one who said it was quite difficult, isn't some amateur. He's a very well experienced and known engineer in the trade. He doesn't speak from just guessing. So take his word on that. He has the experience and if he says it's difficult, it's difficult.
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Kelly
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Re: Harris FM 20 K pro and con views

Post by Kelly »

NECRAT wrote:
Tue Jun 09, 2020 7:28 am
alleo wrote:
Mon Jun 08, 2020 2:27 pm
According to Bob Brown its a miner change most of it done with use of a ruler inside the PA cavity .
That may be, but ChuckG, the one who said it was quite difficult, isn't some amateur. He's a very well experienced and known engineer in the trade. He doesn't speak from just guessing. So take his word on that. He has the experience and if he says it's difficult, it's difficult.
I'll vouch for ChuckG. The 10KW QEI rigs were touchy enough when tuned on frequency. Trying to run one by just changing the exciter frequency = Rapid meltdown, if it would run at all...
Skype:kellyalford Twitter: @KellyAlford

level42
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Re: Harris FM 20 K pro and con views

Post by level42 »

Counterpoint, the QEI rigs, while certainly not the best built transmitters, have a very simple grounded grid tube cavity that is very easy to retune. I have done two of them, both still in service. Replace the factory IPA and exciter with something better, make sure all HV connections are very tight, keep them clean and cool with clean power and they will run just as well as any CCA, McMartin, or similar design.

The FM20K on the other hand, quite an involved frequency change, that is not always an exact science, and as others have mentioned, prepare for some booms! Also, lots of expensive or unattainable proprietary parts (though not as bad as an HT).

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