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#1
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use standoffs between SSB coax and backstay??
On Thu, 06 Nov 2003 09:29:20 -0500, Glenn Ashmore
wrote: It was probably GTO-15. I would hope that who ever went to the trouble of adding the standoffs would know the difference. GTO is hard to tell from RG59 from a distance. Neon sign suppliers even have it in decorator colors. What the hell is GTO-15, some West Marine $20/ft trick? This isn't a neon sign with 40KV of 60 Hz on it....IT'S RF! All the insulation in the world isn't going stop the RF from leaking out, like it's 'spozed ta. Lionheart's tuner is hooked to its backstay with a stainless strap in a gentle curve held on with a stainless hose clamp. Now that we got the damned steel cable holdin' the boom up replaced with something that DOESN'T suck off the HF signal into the mainmast, it works much better......well, at least until the sun exploded wiping out the ionosphere.... 73 DE W4CSC NNNN AR |
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#2
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use standoffs between SSB coax and backstay??
GTO-15 is 15KV insulated wire and fairly standard for tuner to backstay
leads. More for safety than efficiency. The whole idea of elevated lower insulator on the backstay is to prevent some dumb crew member from grabbing a hot lead and getting an RF burn. The GTO limits that possibility. The stainless strap approaching at an angle is probably more efficient and neater looking but gives no protection. West Moron dropped it from the Catalog this year but used to sell it for $1/ft. It is standard material in neon shops for $.50/ft and from HVAC dealers as spark igniter wire for $.25/ft. Larry W4CSC wrote: On Thu, 06 Nov 2003 09:29:20 -0500, Glenn Ashmore wrote: It was probably GTO-15. I would hope that who ever went to the trouble of adding the standoffs would know the difference. GTO is hard to tell from RG59 from a distance. Neon sign suppliers even have it in decorator colors. What the hell is GTO-15, some West Marine $20/ft trick? This isn't a neon sign with 40KV of 60 Hz on it....IT'S RF! All the insulation in the world isn't going stop the RF from leaking out, like it's 'spozed ta. Lionheart's tuner is hooked to its backstay with a stainless strap in a gentle curve held on with a stainless hose clamp. Now that we got the damned steel cable holdin' the boom up replaced with something that DOESN'T suck off the HF signal into the mainmast, it works much better......well, at least until the sun exploded wiping out the ionosphere.... 73 DE W4CSC NNNN AR -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
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#3
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use standoffs between SSB coax and backstay??
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#4
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use standoffs between SSB coax and backstay??
I guess you must have forgotten about your numerous posts
a long time ago (1 year +) where you expoused the use of GTO-15 when feeding your entire rig. Must have been a senior moment. Doug, k3qt s/v Callista "Larry W4CSC" wrote in message ... On Thu, 06 Nov 2003 09:29:20 -0500, Glenn Ashmore wrote: It was probably GTO-15. I would hope that who ever went to the trouble of adding the standoffs would know the difference. GTO is hard to tell from RG59 from a distance. Neon sign suppliers even have it in decorator colors. What the hell is GTO-15, some West Marine $20/ft trick? This isn't a neon sign with 40KV of 60 Hz on it....IT'S RF! All the insulation in the world isn't going stop the RF from leaking out, like it's 'spozed ta. Lionheart's tuner is hooked to its backstay with a stainless strap in a gentle curve held on with a stainless hose clamp. Now that we got the damned steel cable holdin' the boom up replaced with something that DOESN'T suck off the HF signal into the mainmast, it works much better......well, at least until the sun exploded wiping out the ionosphere.... 73 DE W4CSC NNNN AR |
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#5
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use standoffs between SSB coax and backstay??
Doug,
Holding those of us on the senior circuit to what we said in the past is simply not fare. Regards, Ron (I think?) |
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#6
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use standoffs between SSB coax and backstay??
Wasn't me. I never heard of GTO-15 before.....??????
On Thu, 6 Nov 2003 23:24:08 -0500, "Doug Dotson" wrote: I guess you must have forgotten about your numerous posts a long time ago (1 year +) where you expoused the use of GTO-15 when feeding your entire rig. Must have been a senior moment. Doug, k3qt s/v Callista "Larry W4CSC" wrote in message ... On Thu, 06 Nov 2003 09:29:20 -0500, Glenn Ashmore wrote: It was probably GTO-15. I would hope that who ever went to the trouble of adding the standoffs would know the difference. GTO is hard to tell from RG59 from a distance. Neon sign suppliers even have it in decorator colors. What the hell is GTO-15, some West Marine $20/ft trick? This isn't a neon sign with 40KV of 60 Hz on it....IT'S RF! All the insulation in the world isn't going stop the RF from leaking out, like it's 'spozed ta. Lionheart's tuner is hooked to its backstay with a stainless strap in a gentle curve held on with a stainless hose clamp. Now that we got the damned steel cable holdin' the boom up replaced with something that DOESN'T suck off the HF signal into the mainmast, it works much better......well, at least until the sun exploded wiping out the ionosphere.... 73 DE W4CSC NNNN AR Larry W4CSC "Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!" |
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#7
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use standoffs between SSB coax and backstay??
Thanks to all for the discussion. For the minimal effort and expense it
sounds like a good way to save a bit of transmit power. Sorry about the reference to "coax". As I'm not very knowledgeable about these things I couldn't really state what type of wire it was and just guessed coax. Thanks for pointing out the correct wire to use. I don't think my boat currently has this. "Gordon Wedman" wrote in message news:JMfqb.136245$EO3.29023@clgrps13... The other day I was wandering around one of our marinas trying to steal ideas from other boats and I came across an aluminum pilot-house sloop that may have come over from Europe. I noticed that the SSB coax was held away from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've never seen this before and the previous owner didn't do it on my boat. I've been thinking of upgrading the ancient SSB system on my boat and was wondering if these standoffs were something recommended. Anyone know about these? Thanks Gord |
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#8
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use standoffs between SSB coax and backstay??
On Wed, 05 Nov 2003 23:32:57 GMT, "Gordon Wedman"
wrote: The other day I was wandering around one of our marinas trying to steal ideas from other boats and I came across an aluminum pilot-house sloop that may have come over from Europe. I noticed that the SSB coax was held away from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've never seen this before and the previous owner didn't do it on my boat. I've been thinking of upgrading the ancient SSB system on my boat and was wondering if these standoffs were something recommended. Anyone know about these? Thanks Gord Any time the output antenna "hot" of an HF tuner is near anything metal, a capacitor is formed between the antenna wire and the metal objects. This capacitor is in parallel with the output of the transmitter and must be minimized. If it becomes a substantial capacitor (wire close to object), the output tuning capacitor in the tuner will run out of range (low as it goes) and the antenna won't tune properly, especially on the upper frequencies. So, we isolate the wire as far as practical from all metal objects, especially large, grounded metal objects. It is also very important that the antenna lead on the antenna side of the tuner be STABLE, and not flopping around, which causes this natural capacitance to anything to CHANGE during transmissions. If the wire is moving around near metal objects, the shunt capacitance constantly changes, ruining the tune of the tuner. So, this boat had a proper installation.....isolated on long insulators with many of them that would hold the wire stable as it traversed the sheet metal. The effects of shunt capacitance in any HF antenna situation with long wires is on the OTHER end of the antenna from the feed point.....at the insulator at the top of the backstay. This point in the antenna is the highest impedance (nearly infinity we hope) point of the system. The voltage at the upper insulator of a shorter-than-quarter-wave wire is always very high. Any capacitance to a metal object causes a lot of the signal to be shunted off to that object, and mostly lost, wasted. So, it is very important to make sure the upper insulator is NOT installed too near the masthead, but back down the backstay a ways and the upper end of the insulated backstay is never near metal objects, like boom lifting devices made of stainless cable, etc. The tuning of the backstay will go all crazy every time one of these metal cables moves near the upper end of the backstay. We Geoffrey acquired Lionheart, an Amel Sharki 41 ketch, the owner reported the insulated backstay antenna didn't work very well and he never found out why. After I took it over I noted how close the boom lift was to the backstay when the boom was on centerline, where it made my signal on HF just SUCK! So, we changed out the metal cable for insulated line. HF signals are now very acceptable no matter where the mainsail ends up. Getting the metal away from the antenna's upper end high impedance point solved the problem. |
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