fork handle does it again

[bob85]

One of my locals just swapped his penetrator P500 for a new max 2000 due to the winds we have had recently,

first time around he bolted the IMAX straight to his mast bolted to his house outside the shack window,
ground rod in yard connected to mast & taped his coax to the mast ,

He had rfi issues flattening his cctv cameras & bad RF feedback/buzzing on his audio as he wound it up towards 300w FM ,
clearly there was something different about the IMAX that created havoc with rfi at way below what he could run with the p500 all else been equal,

He took little convincing of what his problem likely was & how we fixed my other buddies unusable IMAX install,

off he went to knights for a radial kit, bought a Trenching spade for the fiberglass handle & we wound a 5 turn 4-1/4" choke from g3txq's chart on his rg213 tie wrapped around the isolator/handle,

His signal went up 1/2 s-unit to me & he can run 1200w FM with no cctv issues or hint of rfi/buzzing in his audio,
ACOM amplifier says reflected power/vswr went down a little too .

 

[sp5it]

1200W in FM? This antenna won't handle it long.
Mike

 

[bob85]

sirio 827's won't handle that for long either but that's not my problem,
ACOM protection has been called into service locally,

when your 827 goes open circuit & arcs at the coil connections it frys your coax & shuts amp down,
so far nobody smoked an imax but i imagine if they got long winded on FM at full tilt they would,
im sure the guys running ACOM 2100 & 2000 can't use full power FM for long on any of the end fed base antennas we can buy here in a shop.

 

[RT431]

Personally, I would have kept the P500, much better antenna. Wish I still had mine.

 

[bob85]

The p500 only came down because of the high winds, he does not want a broken p500, they cost double what an IMAX costs here,

if the isolation had not fixed his issue the p500 would have gone straight back up wind or no wind.

Just before I set out to help my local, another local hamster jumped in with the usual radials & chokes don't do anything useful,
another started waffling about resonance & swr been the cause of coax radiating, claiming that resonance is EVERYTHING to do with vswr & your coax radiating

he was getting irate because i told him he was wrong,

that is a common assumption from people with no actual experience or don't wind the right choke for the job or have a hard on for anything starting with FT240-xx ( better but not essential for a single narrow band & not free )

they try a hamster universe ugly balun, its WAY wrong for 27mhz so chokes don't work,
they put radials on without isolation & that don't work so radial kits are useless,
try to use chokes without radials or alternative path for currents, that won't work either,

some stations never had cmc in a magnitude that caused issues or spoiled their radiation pattern so whatever they do is won't make any notable change,
unless of course they are unlucky enough to resonate the line with a reactive choke to create a lower impedance cmc path. ( even that's easy to fix ),

fork handle strikes again,
another station that can run full power on his cmc monster IMAX without any rfi in the shack,

No FT240-xx were harmed in this cmc fix.