Hi, at work I maintain a number of Low-Band (70Mhzish) systems, one of which
runs a Storno exciter at about 15w into a 100w Kathrein linear amplifier.
These are on continous transmit 24/7, last year one appeared to have died
after an air conditioning failure so I went out to the site with the one
spare (still wrapped in polythene)....
On examining the faulty PA I found a fuse holder had arced a little,
probably agravated by a slight loss in spring tension... a quick scrub of
the holder and a new fuse and it was back on the air. So the unused spare PA
got put back into stores! Not bad when you consider that you consider that a
number of these have been on continuous transmit for over 20 years....there
is a hot standby on every site but other than for periodic checks they never
get RF throught them.
I may be able to find a schematic, but it may be a good idea to look on the
net, the manufacturer is Kathrein (better known for VHF FM broadcast stuff).
It is feasible that some scrap ones may already be on the market in the UK,
obviously they will need relays around them to take care of the TX/RX path
but they do have the merit of having integral power supply, metering and
circulators etc.
Probably one of the secrets to their reliability is that nearly the entire
front panel is heatsink..
Beware that I expect the linear PA is unusual for this manufacturer...
regards David
----- Original Message -----
From: <amps-request@contesting.com>
To: <amps@contesting.com>
Sent: Sunday, July 02, 2006 3:03 AM
Subject: Amps Digest, Vol 43, Issue 5
> Send Amps mailing list submissions to
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> Today's Topics:
>
> 1. Re: Maximum RF output in practical application: 4-250A
> (R L Measures)
> 2. Re: Serious transformer problem (John E.Cleeve)
> 3. Plate Load (Mike(W5UC) & Kathy(K5MWH))
> 4. Re: Plate Load (Mike(W5UC) & Kathy(K5MWH))
> 5. Re: Plate Load (Mike(W5UC) & Kathy(K5MWH))
> 6. Re: Maximum RF output in practical application: 4-250A
> (wc6w@juno.com)
> 7. Re: 70MHz transistor PA, schematics?? (wc6w@juno.com)
> 8. Collective Thank You for your help.... (Ken)
> 9. Re: 70MHz transistor PA, schematics?? (crawfish)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 1 Jul 2006 08:06:48 -0700
> From: R L Measures <r@somis.org>
> Subject: Re: [Amps] Maximum RF output in practical application: 4-250A
> To: "W.F van Wyk" <zs6arf@telkomsa.net>
> Cc: amps@contesting.com
> Message-ID: <2AF7E8A5-3765-4646-8669-ADEF70E3119F@somis.org>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> W. F. --- With its max peak emission of 1.3a and a 4500v anode supply
> using g-g config., my guess is that a 4-250A has enough stuff to do
> 1000w-out PEP in SSB service provided that it is tuned up with a
> tuning pulser - or 50wpm dits, and the operator does not speak too
> loudly into the mic.
>
> On Jul 1, 2006, at 6:15 AM, W.F van Wyk wrote:
>
>> I have been hearing claims at the local flea markets here in South
>> Africa
>> that a single 4-250A valve is capable of between 800 - 900 watts in
>> ham band
>> amplifier application.
>>
>>
>>
>> Now I have used these myself in a number of homebrew amplifiers,
>> and never
>> have I even come close to that type of output from a single 4-250A.
>>
>>
>>
>> Have I missed something in my amplifier education or is this High
>> Grade
>> Fertilizer which I currently believe it is.
>>
>>
>>
>> The local experts claiming this indicate voltages on the plate in
>> the region
>> of 5,000 Volts and get a blank look when I enquire about IMD and
>> splatter.
>>
>>
>>
>> Now I am aware on the specification sheets for this valve RF power
>> above 800
>> watts are indicated under certain conditions but I still have to
>> see that
>> put into practice in a Ham amplifier say for normal HF band usage.
>>
>>
>>
>> Please steer me in the right direction here.
>>
>>
>>
>> Thank You
>>
>>
>>
>> Wynand van Wyk (ZS6ARF)
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
> R L MEASURES, AG6K. 805-386-3734
> r@somis.org
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 01 Jul 2006 21:00:06 +0100
> From: John E.Cleeve <g3jvc@jcleeve.idps.co.uk>
> Subject: Re: [Amps] Serious transformer problem
> To: 'Tom W8JI' <w8ji@w8ji.com>
> Cc: amps@contesting.com
> Message-ID: <37e1312425cc234f9e0ad6a8a76407c2@webmail.free-online.net>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Tom, these people may well be audiophiles, however their paper is
> entitled "Suppression of powerline noise, with isolation transformers"
> was presented by B.C.Gabrielson & M.J. Reimold at EMC Expo 87, May 19-
> 21, San Diego....and available on the internet....John G3JVC.
>
>
> On Sat Jul 1 14:02 , 'Tom W8JI' <w8ji@w8ji.com> sent:
>
>>> the secondary. This beast is heavy, and you need a fork
>>> lift to move it. The reason I specified two electrostatic
>>> screens is that in an American paper I read, on the
>>> internet, on feeding AC supplies to EMC/Faraday screened
>>> rooms, one or two isolation transformers were recommended,
>>> with two electrostatic screens per transformer, the
>>> reasoning being complex, so I just accepted it.....
>>
>>The Internet is like Alice's resturant. We can find almost
>>anything we want on the Internet. A portion of it will be
>>accurate, much will not. Especially when it is something
>>designed to sell a certain product, or a clan or clique
>>thing like AudioPhool technical papers.
>>
>>..I also had a proper ground system laid, by a firm of
>>lightning
>>> protection specialists...certified ground resistance now
>>> just 2.1ohms...the
>>
>>What does that have to do with RF noise, which is what we
>>hear on receivers?
>>
>>> incoming public supply is taken to the primary winding of
>>> the isolation transformer, the output, via a screened
>>> lead, to the shack. Both electrostatic sceens are taken
>>> back to the newly installed ground system, and there are
>>> now no connections between the public supply and my
>>> shack....the result, all the electrical noise has now
>>> gone, and apart from the radiated occasional radiated
>>> emissions, my radio background noise has dropped back to
>>> that of 40 years ago...
>>
>>You might have revisited the shack equipment, antennas, and
>>connections before going through all those expensive
>>solutions.
>>
>>The only noise that can "get into" our receivers is RF
>>noise. The only way in should be through the antenna
>>connections. Any other path should easily be down 100dB or
>>more.
>>
>>I'd have looked at then installation of my feedlines and
>>their interface to antennas first.
>>
>>>.In text books of that time, the electrostatic screen was
>>>described as a method of preventing the feed back of
>>>interference into the public supply, by the consumer,
>>>however, it was explained to me, by my local transformer
>>>manufacturer, that it was only looked upon as a safety
>>>measure, by the transformer manufacturers,
>>
>>The manufacturers are correct. It primarily is a safety
>>device. So is bonding transformer laminations at ONE common
>>point and grounding them there, with all other areas of the
>>lamainations insulated.
>>
>>>with the improved high termperature varnishes for the wires
>>>used in winding, they could save a small amount of money,
>>>by not including the copper electrostatic screens....which
>>>may be, why our received noise levels have been climbing in
>>>the past decades
>>
>>Lack of shields in transformers has not increased noise. The
>>noise increase is because of the increase in mains voltages,
>>and because switching supplies and similar RF producing
>>devices have increased.
>>
>>A primary shield is actually very little assurance noise
>>doesn't get through a system. It's a cheap additional
>>band-aid when initially winding a transformer, but the
>>problem is a lack of suitable line bypass capacitors and
>>small series chokes.
>>
>>Anything you did with that big heavy expensive transformer
>>at radio frequencies, I can do better with something I can
>>hold in one hand....and at 10% of the cost.
>>
>>You really ought to learn why your radio system is partially
>>using the power mains as an antenna. That's the real
>>question.
>>
>>When radios were built on an unshielded wooden chassis, when
>>bypass caps were expensive and erratic radio frequency
>>impedances, before we had ferrites and other modern
>>components, and before good components at radio frequencies
>>were obtainable, things were done differently. Solutions
>>necessary back then are very often totally meaningless
>>today. The key is always understanding how things actually
>>work, and not relying on accidents to patch problems.
>>
>>73 Tom
>>
>>
>>--
>>This email has been verified as Virus free
>>Virus Protection and more available at http://www.plus.net
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 1 Jul 2006 15:07:01 -0500
> From: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
> Subject: [Amps] Plate Load
> To: "AMPS" <amps@contesting.com>
> Message-ID: <00d901c69d49$eabc72f0$0300a8c0@HOUSE>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Good Afternoon All:
>
>While we are exercising all of this grey matter on IMD etc, please allow me
>to ask a similar question. If the calculated Plate load Impedence is 1333
>ohms, and the tank circuit looks more like 2100 ohms, how does this affect
>efficiency?
>
> 73,
> Mike, W5UC
>
> http://members.cox.net/w5uc
>
> ------------------------------
>
> Message: 4
> Date: Sat, 1 Jul 2006 15:21:38 -0500
> From: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
> Subject: Re: [Amps] Plate Load
> To: "AMPS" <amps@contesting.com>, "Tom W8JI" <w8ji@w8ji.com>
> Message-ID: <00e801c69d4b$f508f1f0$0300a8c0@HOUSE>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> Ok, then what happens if the tank circuit is designed to match the Plate
> impedence?
>
>
> http://members.cox.net/w5uc
> ----- Original Message -----
> From: "Tom W8JI" <w8ji@w8ji.com>
> To: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
> Sent: Saturday, July 01, 2006 3:19 PM
> Subject: Re: [Amps] Plate Load
>
>
>>> While we are exercising all of this grey matter on IMD etc, please allow
>>> me to ask a similar question. If the calculated Plate load Impedence is
>>> 1333 ohms, and the tank circuit looks more like 2100 ohms, how does this
>>> affect efficiency?
>>
>> Linearity will probably be poor. Efficiency will be high.
>>
>>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 1 Jul 2006 15:45:51 -0500
> From: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
> Subject: Re: [Amps] Plate Load
> To: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>, "AMPS"
> <amps@contesting.com>, "Tom W8JI" <w8ji@w8ji.com>
> Message-ID: <00f701c69d4f$5731da60$0300a8c0@HOUSE>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Tom, please let me rephrase that. I assume from your previous answer that
> if the tank circuit is designed to match the load impedence, then
> linearity
> will improve. What, then, happens to efficiency? I am in the process of
> building a pair of Gi-7bt's for 6 meters. There, linearity is of some
> concern. Once I get that amp on the air, I plan to build a pair of
> Gi-46b's
> for 160. On 160 I couldn't care less about linearity as I rarely, if ever
> work anything but CW, and efficiency is the priority.
>
> 73,
> Mike
>
> http://members.cox.net/w5uc
> ----- Original Message -----
> From: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
> To: "AMPS" <amps@contesting.com>; "Tom W8JI" <w8ji@w8ji.com>
> Sent: Saturday, July 01, 2006 3:21 PM
> Subject: Re: [Amps] Plate Load
>
>
>> Ok, then what happens if the tank circuit is designed to match the Plate
>> impedence?
>>
>>
>> http://members.cox.net/w5uc
>> ----- Original Message -----
>> From: "Tom W8JI" <w8ji@w8ji.com>
>> To: "Mike(W5UC) & Kathy(K5MWH)" <w5uc@cox.net>
>> Sent: Saturday, July 01, 2006 3:19 PM
>> Subject: Re: [Amps] Plate Load
>>
>>
>>>> While we are exercising all of this grey matter on IMD etc, please
>>>> allow
>>>> me to ask a similar question. If the calculated Plate load Impedence
>>>> is
>>>> 1333 ohms, and the tank circuit looks more like 2100 ohms, how does
>>>> this
>>>> affect efficiency?
>>>
>>> Linearity will probably be poor. Efficiency will be high.
>>>
>>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Sat, 1 Jul 2006 22:20:32 GMT
> From: "wc6w@juno.com" <wc6w@juno.com>
> Subject: Re: [Amps] Maximum RF output in practical application: 4-250A
> To: amps@contesting.com
> Message-ID: <20060701.152113.19107.329026@webmail50.lax.untd.com>
> Content-Type: text/plain
>
> Wynand & Rich,
>
> In an impractical application, a Kahn envelope elimination and
> restoration amplifier, the 4-250A is capable of a smidge over 2KW PEP
> just as in plate modulated AM operation. The max plate voltage in
> this instance would be 6KV but, only intermittently.
>
> 73 & Good afternoon,
> Marv WC6W
>
> -- R L Measures <r@somis.org> wrote:
> W. F. --- With its max peak emission of 1.3a and a 4500v anode
> supply
> using g-g config., my guess is that a 4-250A has enough stuff to do
> 1000w-out PEP in SSB service provided that it is tuned up with a
> tuning pulser - or 50wpm dits, and the operator does not speak too
> loudly into the mic.
>
> On Jul 1, 2006, at 6:15 AM, W.F van Wyk wrote:
>
>> I have been hearing claims at the local flea markets here in South
>> Africa
>> that a single 4-250A valve is capable of between 800 - 900 watts
> in
>> ham band
>> amplifier application.
>>
>>
>>
>> Now I have used these myself in a number of homebrew amplifiers,
>> and never
>> have I even come close to that type of output from a single 4-250A.
>>
>>
>>
>> Have I missed something in my amplifier education or is this High
>> Grade
>> Fertilizer which I currently believe it is.
>>
>>
>>
>> The local experts claiming this indicate voltages on the plate in
>> the region
>> of 5,000 Volts and get a blank look when I enquire about IMD and
>> splatter.
>>
>>
>>
>> Now I am aware on the specification sheets for this valve RF power
>> above 800
>> watts are indicated under certain conditions but I still have to
>> see that
>> put into practice in a Ham amplifier say for normal HF band usage.
>>
>>
>>
>> Please steer me in the right direction here.
>>
>>
>>
>> Thank You
>>
>>
>>
>> Wynand van Wyk (ZS6ARF)
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
> R L MEASURES, AG6K. 805-386-3734
> r@somis.org
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> ________________________________________________________________________
> Try Juno Platinum for Free! Then, only $9.95/month!
> Unlimited Internet Access with 1GB of Email Storage.
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>
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sat, 1 Jul 2006 22:20:30 GMT
> From: "wc6w@juno.com" <wc6w@juno.com>
> Subject: Re: [Amps] 70MHz transistor PA, schematics??
> To: knaap159@zonnet.nl, amps@contesting.com
> Message-ID: <20060701.152113.19107.329025@webmail50.lax.untd.com>
> Content-Type: text/plain
>
> Hi Dick,
> Try searching for some of the oollllld Motorola app. notes. -- mid
> 1970's.
>
> They created some circuits for low VHF applications when
> transistors were young.
>
> 73 & Good afternoon,
> Marv WC6W
>
>
> -- "Dick" <knaap159@zonnet.nl> wrote:
>
>
>
> Hello all,
>
> I'm looking for schematics for 70MHz transistorized power amplifiers.
> Sofar I can find some for 50MHz but nothing for 70MHz.
> Any one?
>
> 73
>
> Dick
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> ________________________________________________________________________
> Try Juno Platinum for Free! Then, only $9.95/month!
> Unlimited Internet Access with 1GB of Email Storage.
> Visit http://www.juno.com/value to sign up today!
>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Sat, 01 Jul 2006 18:14:44 -0700
> From: Ken <kloc@commspeed.net>
> Subject: [Amps] Collective Thank You for your help....
> To: amps@contesting.com
> Message-ID: <5.2.1.1.2.20060701180754.016eaad0@mail.commspeed.net >
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> I would like to thank all in the group that helped me during this 4-1000A
> amplifier
> deck restoration. I know I would not be in the position I'm in right now,
> without all
> your input and suggestions. Completed project can be seen at:
>
> http://pg.photos.yahoo.com/ph/wa4mnt/album?.dir=/f5d6scd
>
> Thanks,
>
> ken, wa4mnt
>
>
>
> ------------------------------
>
> Message: 9
> Date: Sat, 1 Jul 2006 21:02:39 -0500
> From: "crawfish" <crawfish@surfmore.net>
> Subject: Re: [Amps] 70MHz transistor PA, schematics??
> To: wc6w@juno.com, knaap159@zonnet.nl, amps@contesting.com
> Message-ID: <002701c69d7b$9a09a760$8f52fea9@default>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I would imagine that the RSGB VHF-UHF Manuals would have some designs.
> Joe W4AAB
> ----- Original Message -----
> From: <wc6w@juno.com>
> To: <knaap159@zonnet.nl>; <amps@contesting.com>
> Sent: Saturday, July 01, 2006 5:20 PM
> Subject: Re: [Amps] 70MHz transistor PA, schematics??
>
>
>> Hi Dick,
>> Try searching for some of the oollllld Motorola app. notes. -- mid
>> 1970's.
>>
>> They created some circuits for low VHF applications when
>> transistors were young.
>>
>> 73 & Good afternoon,
>> Marv WC6W
>>
>>
>> -- "Dick" <knaap159@zonnet.nl> wrote:
>>
>>
>>
>> Hello all,
>>
>> I'm looking for schematics for 70MHz transistorized power amplifiers.
>> Sofar I can find some for 50MHz but nothing for 70MHz.
>> Any one?
>>
>> 73
>>
>> Dick
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
>> ________________________________________________________________________
>> Try Juno Platinum for Free! Then, only $9.95/month!
>> Unlimited Internet Access with 1GB of Email Storage.
>> Visit http://www.juno.com/value to sign up today!
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
>
> ------------------------------
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
> End of Amps Digest, Vol 43, Issue 5
> ***********************************
>
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