Thanks Roger.
I've downloaded the paper, which is relevant not just to this project, but to
our operations in general. At the time of the year when rains (and
thunderstorms) haven't quite started, the wind accumulates sufficient voltage
in the 80m dipole to cause an arc between the two sides of the PL-480,
repeating every 5 or 10 seconds. Quite painful, actually, until you know it's
there. And something that destroyed one of our antenna analyzers.
73,
Jeff
tz4am@aol.com
-----Original Message-----
From: Roger (K8RI) <k8ri@rogerhalstead.com>
To: tz4am <tz4am@aol.com>; amps <amps@contesting.com>
Sent: Wed, Mar 7, 2018 8:59 am
Subject: Re: [Amps] Amp for 444 mHz
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%7Cgener
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@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@aol.com
>
>
> -----Original Message-----
> From: Roger (K8RI) <k8ri@rogerhalstead.com>
> To: tz4am <tz4am@aol.com>; amps <amps@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@aol.com <mailto:tz4am@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@aol.com <mailto:tz4am@aol.com>
> >
> >
> > -----Original Message-----
> > From: Roger (K8RI) <k8ri@rogerhalstead.com
> <mailto:k8ri@rogerhalstead.com>>
> > To: amps <amps@contesting.com <mailto:amps@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@aol.com <mailto:tz4am@aol.com>
> <mailto:tz4am@aol.com <mailto:tz4am@aol.com?>> > >
> > _______________________________________________ > Amps mailing list >
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> <mailto:Amps@contesting.com <mailto:Amps@contesting.com?>> >
> > http://lists.contesting.com/mailman/listinfo/amps > -- Roger (K8RI)
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>
> --
> Roger (K8RI)
>
>
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--
Roger (K8RI)
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