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281. Re: [TenTec] OT: coax versus parallel wire (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 20:21:27 -0600
Its probably on the wide side, just means the feedline gets to help with the radiation more than if it was closer spaced. If you aren't annoyed by computer hash from appliances or 10m TVI, I'd keep o
/archives//html/TenTec/2008-06/msg00220.html (9,118 bytes)

282. Re: [TenTec] OT: coax versus parallel wire (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 20:32:21 -0600
Nice sturdy stuff. Loss should be reasonable up through UHF anyway, better than coax, though 250 ohms isn't quite a handy value for a simple coaxial balun to match to a 50 ohm transmitter... but its
/archives//html/TenTec/2008-06/msg00221.html (9,289 bytes)

283. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 11 Jun 2008 11:23:19 -0600
The loss probably depends on the insulation and its color. Probably PVC insulation will be less loss than rubber, and I'd think white might be less loss than black (thinking a white oxide as the insu
/archives//html/TenTec/2008-06/msg00234.html (9,757 bytes)

284. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 11 Jun 2008 11:33:43 -0600
Two pieces of 75 ohm coax in parallel (corresponding conductors connected together at each end) gives 37.5 ohms. Two sets of those in push-pull gives 75 ohms shielded balanced. Or the same with 50 oh
/archives//html/TenTec/2008-06/msg00235.html (11,949 bytes)

285. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 11 Jun 2008 11:41:48 -0600
In short lengths, so long as the coax wasn't tied to a metal structure, coax connected between balanced loads might not cause much unbalance despite the lack of symmetry in the coax. Certainly the co
/archives//html/TenTec/2008-06/msg00236.html (10,251 bytes)

286. Re: [TenTec] OT: coax versus parallel wire (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 08:01:13 -0600
Until the spacing gets to radiating, a wider spacing for a particular conductor size has less loss because the higher impedance leads to lower current, providing the line is matched. I've heard (once
/archives//html/TenTec/2008-06/msg00239.html (9,944 bytes)

287. Re: [TenTec] OT: coax versus parallel wire (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 08:13:43 -0600
I used to have an 80 meter double extend Zepp in the air. It was made of telephone company spiral bronze strip wrapped direct burial cable, and 1" spaced #18 copperweld (a commercial line). The flat
/archives//html/TenTec/2008-06/msg00240.html (9,552 bytes)

288. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 08:53:08 -0600
Rubber insulated zip cord was the worst for RF loss and for not standing up to weather and light. I vividly recall a clock starting to smoke one evening at home when the rubber zip cord fell apart fr
/archives//html/TenTec/2008-06/msg00241.html (11,722 bytes)

289. Re: [TenTec] TT Centurion (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 16:14:38 -0600
The getter is active, its deposited on the inside of the glass. If there are air molecules heating them with the filament causes some circulation within the tube and eventually they wander by the get
/archives//html/TenTec/2008-06/msg00254.html (9,802 bytes)

290. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 17:36:55 -0600
Yes, but the jacket is not made as a RF dielectric, but as a climate protection for the braid and good center conductor insulation that is quite sensitive to sun and ozone. It has no voltage breakdow
/archives//html/TenTec/2008-06/msg00256.html (11,513 bytes)

291. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 12 Jun 2008 17:41:33 -0600
It should. See my post in response to K5KVH created in the last few minutes. I remembered an instance of known RF loss in the jacket of RG-58 coax. Jackets do vary. They have always varied in how the
/archives//html/TenTec/2008-06/msg00257.html (10,955 bytes)

292. Re: [TenTec] "Z" match question (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 13 Jun 2008 22:11:41 -0600
A single 2" diameter toroid of 61 material tends to handle a KW or more according to my ARRL Antenna Book. I'm not a fan of power wire with PVC insulation. Its bulky and and I suspect some PVC is los
/archives//html/TenTec/2008-06/msg00290.html (8,874 bytes)

293. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sat, 14 Jun 2008 19:13:28 -0600
Some antenna designs depend on the connections being as short as possible (like the crossed feed line in the middle of the 8JK) and some common mode chokes involve winding several turns of coax throu
/archives//html/TenTec/2008-06/msg00309.html (11,067 bytes)

294. Re: [TenTec] Power Pole noises (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 15 Jun 2008 11:34:39 -0600
Maybe the lightning was triggered by the arcing on top that pole that made the noise. E.g. a stream of ionized air wafting up from the pole top lowered the breakdown voltage from the cloud above. 73,
/archives//html/TenTec/2008-06/msg00317.html (9,496 bytes)

295. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 17 Jun 2008 08:53:39 -0600
The write up in my ARRL antenna book, 1994 edition pages 15-2 and 15-3 was based on tests made in 1979 with PLASTIC, not rubber cord, type SPT-1 from GC. Losses were high. Losses with rubber were hig
/archives//html/TenTec/2008-06/msg00346.html (10,977 bytes)

296. Re: [TenTec] Solder and my Omni (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 17 Jun 2008 08:57:35 -0600
The good solder wick uses an activated rosin flux. So does good solder. Plain rosin is cheaper but not nearly as good on dirty or oxidized solder. 73, Jerry, K0CQ
/archives//html/TenTec/2008-06/msg00347.html (8,334 bytes)

297. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 17 Jun 2008 09:02:38 -0600
If you can actually buy it by the yard. Many of the exotic coaxes at US distributors are sold only by the 100' or 500' roll. Or you buy it by the roll and sell by the yard, hoping the roll runs out j
/archives//html/TenTec/2008-06/msg00348.html (11,193 bytes)

298. Re: [TenTec] OT 75 Ohm twin feeder (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 18 Jun 2008 09:27:42 -0600
A lossy feed line won't look bad checking SWR at the transmitter. It looks good even when the antenna has fallen down. It should be checked with the antenna end open or shorted, though a short can ra
/archives//html/TenTec/2008-06/msg00365.html (13,741 bytes)

299. Re: [TenTec] OmniVI Plus Over Drive Amp (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 22 Jun 2008 11:27:09 -0600
What you need are TWO Birds. Running them cascaded you will discover that the input Z of a Bird feeding a matched load isn't necessarily a matched load. E.g. the Bird changes the impedance seen. To m
/archives//html/TenTec/2008-06/msg00391.html (11,795 bytes)

300. Re: [TenTec] OmniVI Plus Over Drive Amp (score: 1)
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 22 Jun 2008 17:57:28 -0600
Try two birds in cascade before you are so sure. 73, Jerry, K0CQ
/archives//html/TenTec/2008-06/msg00398.html (12,043 bytes)

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