[Amps] Amp for 444 mHz

Wed Mar 7 03:58:38 EST 2018

45C might be pushing the ambient temp a bit.
For static buildup you might find this paper of interest:
http://apps.geindustrial.com/publibrary/checkout/Arresters?TNR=White%20Papers%7CArresters%7Cgeneric
There are a number of commercially available arrestors.  The solid state 
ones "usually" limit DC (static) to very low values although they can be 
a bit on the expensive side. OTOH they are a lot cheaper than the 
equipment they protect.

Coax from exciter to amp of 50 meters (roughly 162 feet) of lmr-300 
would be a fair amount of loss at 440.  I didn't look it up so I don't 
know the real value at 440.

OTOH SS 440 amps can be found with fairly low drive requirements.

73, Roger (K8RI)

On 3/5/2018 Monday 7:43 PM, tz4am at aol.com wrote:
> Hi Roger:
>
> All good thoughts and no need to apologize. Some issues like static 
> build up need to be addressed.
>
> This would go in a structure already built (top ot stairwell/dead 
> elevator shaft). I think the temp can be kept below 45 degree C.  We 
> can get AC to the site and put the powersupply nearby.
>
> With the coax we can find locally, losses may be high enough that we 
> may not get sufficient power to drive the amp, starting with 45w 
> output and a LMR300 coax and a run of 50 meters or so.
>
> The static issue is something I may want to discuss with you. We're 
> coming to the part of the year (dry, windy) when static buildup in 
> antennas is serious and has already caused us problems with my amateur 
> antennas.
>
> I'll get back to you with more questions later.
>
> With kind regards,
>
> Jeff
>
> tz4am at aol.com
>
>
> -----Original Message-----
> From: Roger (K8RI) <k8ri at rogerhalstead.com>
> To: tz4am <tz4am at aol.com>; amps <amps at contesting.com>
> Sent: Sat, Mar 3, 2018 6:03 am
> Subject: Re: [Amps] Amp for 444 mHz
>
> Remoting does remove loss and at 444MHz that can be substantial, BUT
> nothing comes for free and remote mounting an amp creates new problems.
>
> You probably know all of the following. If so, I apologize, but I'm
> including it just-in-case.
>
> Of course the first that comes to mind is weatherproofing. Protecting
> the amp and PS from the weather, yet keeping it cool with the hot sun
> blazing down. Mali being roughly 17'30" N of the equator and in an arid
> area, I assume that can be really hot, but I also doubt you get many
> thunderstorms, still getting power to the amp requires some attention.
> Static build up is likely a problem.
>
> Even if you only get the occasional TS it requires keeping static from
> the lines to the amp. The PS is "usually" kept close to the amp and
> rarely is DC run from the shack to the remote amp, yet if you have a
> regulated supply that can do remote sensing then it might be possible to
> have the proper voltage at the amp. Without remote sensing the DC
> voltage at a remote amp can change drastically between full load and no
> load.
>
> Just some thoughts.
>
> Oh, I did find some high power amps made in Europe, but they are 
> expensive.
>
> 73, Roger (K8RI)
>
>
> On 3/2/2018 Friday 4:21 PM, tz4am at aol.com <mailto:tz4am at aol.com> wrote:
> > Thanks Roger. All good questions. Base station like net control. Duty
> > cycle not more than 30%. Others have suggested remoting amp to the
> > rooftop location near the antenna.  With that, I think even 100 watts
> > would be fine.
> >
> > tz4am at aol.com <mailto:tz4am at aol.com>
> >
> >
> > -----Original Message-----
> > From: Roger (K8RI) <k8ri at rogerhalstead.com 
> <mailto:k8ri at rogerhalstead.com>>
> > To: amps <amps at contesting.com <mailto:amps at contesting.com>>
> > Sent: Thu, Mar 1, 2018 1:34 pm
> > Subject: Re: [Amps] Amp for 444 mHz
> >
> > SSB? FM? Digital?  What kind of duty cycle?  Mobile or home station?
> > I'm assuming (which is never safe) you want SS. If you are willing to
> > go new there are a number of  SS amps available for FM.  A quick
> > search should turn up quite a few in the 10 to 50W drive and 160 out
> > range. There are a few in the 200W range and it "seems" as if I
> > remember seeing one with 300W out. Back in the 70s I had a complete,
> > self contained, 600W out SS amp.  Wish I'd kept it. Now if you want
> > AB1 for SSB, there are some new SS amps that run up to a KW out, but
> > they are definitely not inexpensive. There are also tube amps that run
> > from 800 to the legal limit. Again a search might find some, new
> > and/or used. There are the Old Henry tube amps that use a 3CX800 that
> > occasionally show up for sale. Availability in EU? Import duty, VAT,
> > and shipping might make one from the US pretty expensive IIRC there
> > are several companies in the EU building tube and SS high power VHF
> > amps. Again, not cheap. Good Luck. 73, Roger (K8RI) On 2/27/2018
> > Tuesday 3:02 PM, Jeff Dorsey via Amps wrote: > Dear All: > > > I need
> > an amp for 444 mHz band, somewhere between 100 and 400 watts output,
> > preferrably from EU but also possibly from USA. > > > With kind
> > regards, > > > Jeff > > > > tz4am at aol.com <mailto:tz4am at aol.com> 
> <mailto:tz4am at aol.com <mailto:tz4am at aol.com?>> > >
> > _______________________________________________ > Amps mailing list >
> > Amps at contesting.com <mailto:Amps at contesting.com> 
> <mailto:Amps at contesting.com <mailto:Amps at contesting.com?>> >
> > http://lists.contesting.com/mailman/listinfo/amps > -- Roger (K8RI)
> > --- This email has been checked for viruses by Avast antivirus
> > software. https://www.avast.com/antivirus
> > _______________________________________________ Amps mailing list
> > Amps at contesting.com <mailto:Amps at contesting.com> 
> <mailto:Amps at contesting.com <mailto:Amps at contesting.com?>>
> > http://lists.contesting.com/mailman/listinfo/amps
>
>
> -- 
> Roger (K8RI)
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
>

-- 
Roger (K8RI)