Re: Topband: Bad tower shunt capacitor
The 3 line sections will handle more (-; And as many BCB and other commercial stations are being dismantled it is available at scrap prices or less. I have several large rolls of 1 5/8 here for sale. Carl KM1H - Original Message - From: Herb Schoenbohm he...@vitelcom.net To: topband@contesting.com; TopBand List topband@contesting.com Sent: Wednesday, January 29, 2014 10:53 PM Subject: Re: Topband: Bad tower shunt capacitor Wouldn't 1 5/8 hardline make a better HV RF capacitor? Herb, KV4FZ On 1/29/2014 11:34 PM, HAROLD SMITH JR wrote: Jamie, The VSWR would change because the arc would change the impedance at the Arc point. From perhaps several hundred or thousand ohms to near Zero during the Arc.. 73, Price W0RI Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3684/7045 - Release Date: 01/30/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Just an update on this - last night FT5ZM was spotted briefly on 160M and I went down to listen for awhile. I didn't hear much and what I did hear I couldn't make myself believe it was them ! So I thought I would try and load up the tower and see if it repeated its bad behavior. I couldn't get outside yesterday - raining and cold. Well, it tuned 1:1 perfectly and I gave it 1000 watts with no difficulties at all. No sudden SWR spikes or any of that. This makes me think the caps are just fine and a connection is flashing over at some point. I didn't push my luck and go for the entire 1500 watts, but I was pleased with this situation. At this point I just need to get into the cap box and reset the connections and tighten everything up. I'll look at the cage wires and make sure nothing is touching where it shouldn't. 73, Jamie WB4YDL Sent from my iPad On Jan 30, 2014, at 10:28 AM, ZR z...@jeremy.mv.com wrote: The 3 line sections will handle more (-; And as many BCB and other commercial stations are being dismantled it is available at scrap prices or less. I have several large rolls of 1 5/8 here for sale. Carl KM1H - Original Message - From: Herb Schoenbohm he...@vitelcom.net To: topband@contesting.com; TopBand List topband@contesting.com Sent: Wednesday, January 29, 2014 10:53 PM Subject: Re: Topband: Bad tower shunt capacitor Wouldn't 1 5/8 hardline make a better HV RF capacitor? Herb, KV4FZ On 1/29/2014 11:34 PM, HAROLD SMITH JR wrote: Jamie, The VSWR would change because the arc would change the impedance at the Arc point. From perhaps several hundred or thousand ohms to near Zero during the Arc.. 73, Price W0RI Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4259 / Virus Database: 3684/7045 - Release Date: 01/30/14 _ Topband Reflector Archives - http://www.contesting.com/_topband -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Look closely and you may see a hairline crack on the bad one. Also look for other possibilities. A number of times I've swapped out bad matching capacitors without solving the problem, only to find later it was simply an oxidized connection that needed to be cleaned up and tightened down. 73/Jon AA1K On 1/29/2014 7:26 PM, James C. Hall, MD wrote: I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? 73, Jamie WB4YDL Sent from my iPad _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Jamie, When I had a problem like that on a matching system, I had someone else key the transmitter and watched the feedpoint at night. It took ten seconds to see the problem ! Fireworks had nothing on what happened. 73 Don, G3BJ / G5W -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of James C. Hall, MD Sent: 30 January 2014 00:27 To: topband@contesting.com Subject: Topband: Bad tower shunt capacitor I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? 73, Jamie WB4YDL Sent from my iPad _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Wouldn't 1 5/8 hardline make a better HV RF capacitor? Herb, KV4FZ On 1/29/2014 11:34 PM, HAROLD SMITH JR wrote: Jamie, The VSWR would change because the arc would change the impedance at the Arc point. From perhaps several hundred or thousand ohms to near Zero during the Arc.. 73, Price W0RI Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Bad tower shunt capacitor
I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? 73, Jamie WB4YDL Sent from my iPad _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
I have an omega matched 120 foot tower and I apparently have a bad vacuum variable capacitor. Upon applying more than about 300 watts, the SWR goes off scale. Tuning it out and trying again, yields the same thing. The question is which capacitor is the culprit. These are surplus Soviet caps obtained from the Ukraine and, as I recall, the larger value capacitor is the parallel one, not the series one. I could buy one of each and switch one at a time and have a spare left over. Any suggestions ? Jamie, How do you know it is a capacitor and not something else? Normally vacuum capacitors are either good, have air, or are shorted. They short when a plate melts and stay shorted in that position or further meshed They have no return pull tension when they have no vacuum If the tuning is changing, maybe something else on the tower is arcing, like an insulator? _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE On Jan 29, 2014, at 4:26 PM, James C. Hall, MD wrote: Any suggestions ? -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Bad tower shunt capacitor
Jamie, The VSWR would change because the arc would change the impedance at the Arc point. From perhaps several hundred or thousand ohms to near Zero during the Arc.. 73, Price W0RI Thanks Steve: Not bad - I may try that ! :) The question in my mind was if there was an arc outside the caps, why would the SWR change ? Anyway, I may be missing something. I haven't been inside the cap box at the tower for many months so I'll get into it - may be something easy. 73, Jamie WB4YDL Sent from my iPad On Jan 29, 2014, at 7:11 PM, wb6r...@mac.com wrote: Have someone hit the key while you watch which one flashes over. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband
