[TowerTalk] 4 square for 80

Sun Sep 25 21:58:35 EDT 2016

Many VHFers and others, put their amps at the base of the antenna for 
that reason.

73, Joe
K2XX

> Guy Olinger <mailto:k2av at contesting.com>
> Sunday, September 25, 2016 8:53 PM
> The 1.5 kW PEP is at the amplifier output.
>
> That has been clarified with the FCC multiple times. Tuner, feedline,
> antenna system losses are your problem. You are diminished by those losses
> unless you either have no losses, or run illegally.
>
> The commercial measurement scheme does not apply to the amateur service
> except for a couple bands where that particular band references effective
> radiated power. 1.5 kW is not allowed on those amateur bands.
>
> 73, Guy K2AV.
>
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> jimlux <mailto:jimlux at earthlink.net>
> Sunday, September 25, 2016 7:07 PM
>
>
> So measure your output power at the system interface to the 
> "antenna".. put 1500 watts (total) into your 4 antennas: sum the 
> powers at each element (including if you have phased them so you have 
> a negative element).  That's what commercial broadcasters do, isn't it?
>
> The regulations don't say "amplifier output", they say
> "PEP (peak envelope power). The average power supplied to the antenna
> transmission line by a transmitter during one RF cycle at the crest of
> the modulation envelope taken under normal operating conditions. "
> "(b) No station may transmit with a transmitter power exceeding 1.5 kW 
> PEP. "
>
> If I define my "antenna transmission line" reference plane at the 
> antenna feed points, I think that works.
>
>
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> Guy Olinger <mailto:k2av at contesting.com>
> Sunday, September 25, 2016 3:05 PM
> On Sun, Sep 25, 2016 at 12:25 PM, Jim Brown <jim at audiosystemsgroup.com>
>
> Noise, yes. Gotta give you that one, but the main reason for the 4 square
> was TX gain, right? You do have listening antennas for 160 and 80? So we
> have to worry about *loss*. Loss eats up gain from patterns. Loss eats up
> amplifier output. Your *system* gain past your transceiver is antenna gain
> + amplifier gain *** minus LOSSES ***.
>
> Diversion of power to miscellaneous conductor paths is almost universally
> lossy and never in directions and modes desired in our attempts at
> directional arrays.
>
> The common mode path on the outside of coax shields is lossy first because
> it has a thick jacket which is never designed for low loss, second because
> it often lays on the ground or is buried, a very lossy situation. Try your
> 20 meter dipole laying on the ground to check that out if you're not
> convinced. And if that is not enough, coax is often taped to towers, 
> making
> it a transformer winding to the metal of the tower, whose reradiation is
> certainly not going to be useful in a 4 square.
>
> In correspondence about FCP conversion projects, I always advise 
> installers
> to ALSO go after all those death by a thousand paper cuts losses, because
> the FCP installers are physically into a lot of the situations where 
> corner
> cutting costs transmitted power.
>
> The first 0.3 dB loss to your brand new 1500 watts out takes away 100
> watts. The second 0.3 dB takes away 93 watts, the third 0.3 dB takes away
> 87 watts. A 1 dB loss drops you to 1192 watts.
>
> So three paper-cut 0.3 dB losses effectively drop your 1500 watt Alpha 
> 9500
> to 1200 watts. If your 1500 watt amp would only put out 1200 when you got
> it from the factory, you would send it back to the factory, right? No? 0.3
> dB losses can't be significant.
>
> "Oh, it's all right, it's only a dB, that's fine, I love my new amp. 1200
> watts is the same as 1500 watts." <smile, smile, warm smile>.
>
> Actually, upon careful reflection, what I think I really heard was
> !@%&*@!!!!! #$@%@%!!!!! #^#$%^!!!!!. <pant> 1200 watts!!!!! <pant,
> pant> Do they think I'm an idiot ???? <pant, pant, pant> <Finger nails
> on chalk board type scream>.
>
> Oh, that's better. For a moment I thought you were overdosed on Elavil.
>
> If you see a preventable 0.3 dB loss, step on it like a roach and kill it
> before it multiplies. Don't put up with any 0.3 dB loss you don't have to,
> and if you do have to put up with it, know *exactly why* you have to. Then
> that 4 dB you can count on actually gettting out of a 4 square for sure,
> regardless, will really mean something. I have a list of nearly thirty
> different ways to waste 0.3 dB of RF energy. When I get done it might be
> more than thirty.
>
> Common mode losses can be way more than 0.3 dB.
>
> Remember.... Death by a thousand paper cuts.....
>
> I won't go into why and when isolation transformers can be be better than
> ferrite based balun and choke type windings. That's a whole other story.
>
> I have a design for an upside down 80m 4 square for mounting around a
> tower, that does not touch the ground, does not involve large RF fields in
> or near the ground, and uses the top Philly-stran guys to support FCP's as
> counterpoises for the upside down verticals, and deals with common mode in
> a way that is definitely out of the traditional "you gotta have 1/4 wave
> radials" box. But it's not ready for general publishing. Anyone interested
> in trying this experimental design, email me off list.
>
> 73, and good luck on the 4 square.
>
> Guy K2AV
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