Re: Topband: 160 m inverted L
David, Thanks for sharing the study. I am trying to digest it. Need to go through it again. He says: " There is an optimal height for an elevated groundplane, that height is not at ground zero, and is typically around 0.05 wavelength. (The statement the higher-the-better is not always true for such systems.) " This figures to a little over 15 feet above ground for 160M. I can manage that. I think he has another study for the added efficiency with a ground screen under elevated radials. I want to find that one too. Bob K6UJ On 11/9/16 9:04 AM, David Cutter wrote: Hello Peter I haven't done any work on this, but Ralph has. Have a look at this site and others of his: http://www.arising.com.au/people/holland/ralph/shortvert.htm David G3UNA - Original Message - From: "Peter Voelpel" To: Sent: Wednesday, November 09, 2016 4:57 PM Subject: Re: Topband: 160 m inverted L Think of a dipole close to the ground, it will not be efficient with all that coupling to earth and resulting losses. 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of David Cutter Sent: Mittwoch, 9. November 2016 17:37 To: Mike Waters; Rob Atkinson; topband Subject: Re: Topband: 160 m inverted L I recall reading from Ralph Holland that 0.015 wavelength was a good height. David G3UNA - Original Message - From: "Mike Waters" To: "Rob Atkinson" ; "topband" Sent: Wednesday, November 09, 2016 4:11 PM Subject: Re: Topband: 160 m inverted L Fifty feet?! That means the feedpoint --the bottom of the antenna-- would be 50 feet up! Do you know how high the top would have to be? I don't agree with that at all. And I've never heard of anyone who ever did that. The four elevated radials in these tests were just 16 feet high! And what is more, the frequencies were 1490, 1450, 1240, and (maybe) 625 KHz. Almost as effective as 120 buried radials. lists.contesting.com/_topband/2007-11/msg00248.html I forget the radial height in Rudy Severns' (N6LF) tests, but IIRC they weren't anywhere near 50' high. My two elevated radials were 10' high. I know that a little higher (and a few more of them) would have been better, but I can tell you that that 160m inverted-L WORKED! And I'm by no means the only one. :-) 73, Mike www.w0btu.com On Wed, Nov 9, 2016 at 6:10 AM, Rob Atkinson wrote: The rule of thumb for effective elevated radial height is 1/10 wavelength, so on 160, around 50 feet up. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Got a lot of mail about this, teaching me to shut up because I don't have much free time. Look folks, as you all know, just about everything with antennas works in some fashion and there's a sliding scale. It's not all black and white. With elevated radials, it isn't as if putting radials at 20 feet up for a 160 m. vertical monopole or 30 feet or anything below 50 feet like 49, will turn them off and make them entirely non-functional. But gradually, as they are placed ever closer to earth, their function as a _counterpoise_ is lessened, and they become more of a _ground system_. You can certainly place them at say, 20 feet high, however, I'd employ more than three or four at that height. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Hello Peter I haven't done any work on this, but Ralph has. Have a look at this site and others of his: http://www.arising.com.au/people/holland/ralph/shortvert.htm David G3UNA - Original Message - From: "Peter Voelpel" To: Sent: Wednesday, November 09, 2016 4:57 PM Subject: Re: Topband: 160 m inverted L Think of a dipole close to the ground, it will not be efficient with all that coupling to earth and resulting losses. 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of David Cutter Sent: Mittwoch, 9. November 2016 17:37 To: Mike Waters; Rob Atkinson; topband Subject: Re: Topband: 160 m inverted L I recall reading from Ralph Holland that 0.015 wavelength was a good height. David G3UNA - Original Message - From: "Mike Waters" To: "Rob Atkinson" ; "topband" Sent: Wednesday, November 09, 2016 4:11 PM Subject: Re: Topband: 160 m inverted L Fifty feet?! That means the feedpoint --the bottom of the antenna-- would be 50 feet up! Do you know how high the top would have to be? I don't agree with that at all. And I've never heard of anyone who ever did that. The four elevated radials in these tests were just 16 feet high! And what is more, the frequencies were 1490, 1450, 1240, and (maybe) 625 KHz. Almost as effective as 120 buried radials. lists.contesting.com/_topband/2007-11/msg00248.html I forget the radial height in Rudy Severns' (N6LF) tests, but IIRC they weren't anywhere near 50' high. My two elevated radials were 10' high. I know that a little higher (and a few more of them) would have been better, but I can tell you that that 160m inverted-L WORKED! And I'm by no means the only one. :-) 73, Mike www.w0btu.com On Wed, Nov 9, 2016 at 6:10 AM, Rob Atkinson wrote: The rule of thumb for effective elevated radial height is 1/10 wavelength, so on 160, around 50 feet up. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Think of a dipole close to the ground, it will not be efficient with all that coupling to earth and resulting losses. 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of David Cutter Sent: Mittwoch, 9. November 2016 17:37 To: Mike Waters; Rob Atkinson; topband Subject: Re: Topband: 160 m inverted L I recall reading from Ralph Holland that 0.015 wavelength was a good height. David G3UNA - Original Message - From: "Mike Waters" To: "Rob Atkinson" ; "topband" Sent: Wednesday, November 09, 2016 4:11 PM Subject: Re: Topband: 160 m inverted L > Fifty feet?! That means the feedpoint --the bottom of the antenna-- would > be 50 feet up! Do you know how high the top would have to be? I don't > agree > with that at all. And I've never heard of anyone who ever did that. > > The four elevated radials in these tests were just 16 feet high! And what > is more, the frequencies were 1490, 1450, 1240, and (maybe) 625 KHz. > Almost > as effective as 120 buried radials. > lists.contesting.com/_topband/2007-11/msg00248.html > > I forget the radial height in Rudy Severns' (N6LF) tests, but IIRC they > weren't anywhere near 50' high. > > My two elevated radials were 10' high. I know that a little higher (and a > few more of them) would have been better, but I can tell you that that > 160m > inverted-L WORKED! And I'm by no means the only one. :-) > > 73, Mike > www.w0btu.com > > On Wed, Nov 9, 2016 at 6:10 AM, Rob Atkinson > wrote: > >> The rule of thumb for effective elevated radial height is 1/10 >> wavelength, >> so on 160, around 50 feet up. >> >> 73 >> >> Rob >> K5UJ >> > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
I recall reading from Ralph Holland that 0.015 wavelength was a good height. David G3UNA - Original Message - From: "Mike Waters" To: "Rob Atkinson" ; "topband" Sent: Wednesday, November 09, 2016 4:11 PM Subject: Re: Topband: 160 m inverted L Fifty feet?! That means the feedpoint --the bottom of the antenna-- would be 50 feet up! Do you know how high the top would have to be? I don't agree with that at all. And I've never heard of anyone who ever did that. The four elevated radials in these tests were just 16 feet high! And what is more, the frequencies were 1490, 1450, 1240, and (maybe) 625 KHz. Almost as effective as 120 buried radials. lists.contesting.com/_topband/2007-11/msg00248.html I forget the radial height in Rudy Severns' (N6LF) tests, but IIRC they weren't anywhere near 50' high. My two elevated radials were 10' high. I know that a little higher (and a few more of them) would have been better, but I can tell you that that 160m inverted-L WORKED! And I'm by no means the only one. :-) 73, Mike www.w0btu.com On Wed, Nov 9, 2016 at 6:10 AM, Rob Atkinson wrote: The rule of thumb for effective elevated radial height is 1/10 wavelength, so on 160, around 50 feet up. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 M Inverted 'L'
Here are some photos of the omega match (L-network) tuner I was referring to earlier. No inductor needed. Visit www.w0btu.com/files/antenna/160m_inv-L and click on 100_3761.JPG there. As I said, that tuner (1) easily handled the full legal limit and (2) the bigger capacitor there was overkill. The plate spacing didn't have to be that wide, but that's all I had on hand. More info about it partway down this page: www.w0btu.com/160_meters.html 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
My elevated radials are now 24m up but sloping. Big difference to before where I tried 4m high radials. I went from a T-vertical to a driven tower with top load as an elevated groundplane some years ago and that is the best transmit antenna I ever used. It is also outstanding on receive. I can hear weak stations with it which are inaudible on my relatively short 160m long beverage. 73 Peter, DJ7WW -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bob K6UJ Sent: Mittwoch, 9. November 2016 16:48 To: topband@contesting.com Subject: Re: Topband: 160 m inverted L thanks Rob, The best I can do in my situation is 10 feet high for the 160M elevated radials. A far cry from 50 feet :-( I will work on maximizing the size of my ground screen under the inverted L. Hopefully this will increase some of the efficiency lost from the low elevated radials. Its tough doing a 160M antenna on a city lot... Bob K6UJ On 11/9/16 4:10 AM, Rob Atkinson wrote: > The rule of thumb for effective elevated radial height is 1/10 > wavelength, so on 160, around 50 feet up. > > 73 > > Rob > K5UJ > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Fifty feet?! That means the feedpoint --the bottom of the antenna-- would be 50 feet up! Do you know how high the top would have to be? I don't agree with that at all. And I've never heard of anyone who ever did that. The four elevated radials in these tests were just 16 feet high! And what is more, the frequencies were 1490, 1450, 1240, and (maybe) 625 KHz. Almost as effective as 120 buried radials. lists.contesting.com/_topband/2007-11/msg00248.html I forget the radial height in Rudy Severns' (N6LF) tests, but IIRC they weren't anywhere near 50' high. My two elevated radials were 10' high. I know that a little higher (and a few more of them) would have been better, but I can tell you that that 160m inverted-L WORKED! And I'm by no means the only one. :-) 73, Mike www.w0btu.com On Wed, Nov 9, 2016 at 6:10 AM, Rob Atkinson wrote: > The rule of thumb for effective elevated radial height is 1/10 wavelength, > so on 160, around 50 feet up. > > 73 > > Rob > K5UJ > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
thanks Rob, The best I can do in my situation is 10 feet high for the 160M elevated radials. A far cry from 50 feet :-( I will work on maximizing the size of my ground screen under the inverted L. Hopefully this will increase some of the efficiency lost from the low elevated radials. Its tough doing a 160M antenna on a city lot... Bob K6UJ On 11/9/16 4:10 AM, Rob Atkinson wrote: The rule of thumb for effective elevated radial height is 1/10 wavelength, so on 160, around 50 feet up. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
The rule of thumb for effective elevated radial height is 1/10 wavelength, so on 160, around 50 feet up. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160 M Inverted 'L'
Folks, You don’t need expensive vacuum capacitors or bread slicers/toast racks to match your 160 metre ‘L’. I use a low pass L-network consisting of 0.95 microhenrys in series and 1600 pF in parallel with the coax. The inductor is not real and is made by slightly extending the length of the antenna, which is 90 ft up and 46 ft horizontal. The 1600 pF cap is made up of several high voltage 6.3 KV disc multilayer ceramic capacitors in parallel. These are readily available and cost 2 or 3 GBP each from CPC/Farnell (CA05041 series made by Murata). I have been using this arrangement for some ten years at significant power levels without any failures. 73, Tom G3OLB _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Agree. I use three fixed serial caps with shorting relays to tune my 160m T, 8 elevated 125' radials, across the full band in 45KHz segments. The antenna is cut for 1820 and fed with a 50::25 TLT. The voltages across each cap (3 all the same value) is well below 400v at QRO so I used surplus 1Kv mica transmit caps from Ukraine. Small relays with 5Kv coil isolation short each cap. SPST 12a DIP relays with very short duplex leads. Never any hot switching so they are ok +4 years. Interestingly the series cap values are all short, one=2000, two=1000, & three=667pf exactly move the needed for ~45KHz frequency, but other combinations might be necessary with other T's. Use EZNEC! I use a rotary switch with diode steering to select relay combos for each segment over a four wire cable. I did shunt each cap with 100k ohms 2w carbon resistor to insure static charge was shared equally. Cost about 10% of a vacuum variable and faster to move freq. Not my idea, thanks to somebody on TB who suggested this - a winner. Grant KZ1W On 11/8/2016 15:12 PM, Herbert Schoenbohm wrote: Bread slicers have their issues and are not really the best solution. Using a fixed high current mica G2 broadcast capacitor of a higher value than you need, and making it variable with a series inductor is the way to go. This is what broadcast stations do in their ATU's. I haven't ever seen a bread slicer in a radio station ATU. A good high current mica cap and a flat wound taped coil IMHO is the way to make everything work well with no breakdowns. For a wide range of matching consider a bridge T with fixed components and taped coils. Go to W8JI's wonderful site for the values you need based on the impedance presented to your feed-line. Herb, KV4FZ On 11/8/2016 6:55 PM, Rob Atkinson wrote: A vacuum variable for L impedance matching is unnecessary. Vacuum variable capacitors leak eventually. It take a long time for them to go through their ranges and you have to have the mechanics outside if you perform remote tuning, to sense or count turns to track when the v.v. is nearing its maximum or minimum. It is far far easier and faster to use an air variable that rotates freely. You only need to keep it sheltered. Elevated radials are fine provided they are high enough to be decoupled from earth, which for most hams is difficult to accomplish on 160 m. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Makes sense Rob. Probably a good approach is to find the capacitance needed and use fixed vacuum caps in lieu of a vacuum variable. Then we have a bullet proof feed sys. Fixed vac caps are plentiful on ebay. I have collected a bunch of them. What height would be adequate for a 160 elevated radial to have decent decoupling ? I think you are right, for most hams, including me, it is hard to get very much height so we must compromise, but we do the best that we can do. Bob K6UJ On 11/8/16 2:55 PM, Rob Atkinson wrote: A vacuum variable for L impedance matching is unnecessary. Vacuum variable capacitors leak eventually. It take a long time for them to go through their ranges and you have to have the mechanics outside if you perform remote tuning, to sense or count turns to track when the v.v. is nearing its maximum or minimum. It is far far easier and faster to use an air variable that rotates freely. You only need to keep it sheltered. Elevated radials are fine provided they are high enough to be decoupled from earth, which for most hams is difficult to accomplish on 160 m. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
I fully agree. And wide plate spacing isn't either, even at the legal limit! I used an omega match (with two capacitors and no inductors) to match the coax to my 160m inverted-L. The largest one in the photo on my site is overkill, it's what I had. 73, Mike www.w0btu.com On Nov 8, 2016 4:55 PM, "Rob Atkinson" wrote: > > A vacuum variable for L impedance matching is unnecessary. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Ive never owned a vacuum variable. What I have been using for decades are very large air variables hung from a stick, or tree or whatever and I cover it up with a 2L pop bottle* with the bottom cut out of it. Fix in place with rope, string, tape, fishing line, whatever. I cant take credit for this trick (I dont think anyways) as I have seen hardline coax splices made much the same way many moons ago at the famous VE1ZZ antenna farm. Its pretty rare for this to ever fail, or even have wx issues. Of course if you get screaming high winds with freezing rain going horizontal it is possible to get a little frozen moisture up inside the bottle and then onto the plates of the cap, but transmitting a few times usually solves the problem. *would the equivalent of 2L pop bottle be ½ gallon soda bottle? Mike VE9AA A vacuum variable for L impedance matching is unnecessary. Vacuum variable capacitors leak eventually. It take a long time for them to go through their ranges and you have to have the mechanics outside if you perform remote tuning, to sense or count turns to track when the v.v. is nearing its maximum or minimum. It is far far easier and faster to use an air variable that rotates freely. You only need to keep it sheltered. Elevated radials are fine provided they are high enough to be decoupled from earth, which for most hams is difficult to accomplish on 160 m. 73 Rob K5UJ Mike, Coreen & Corey Keswick Ridge, NB _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
From: Herbert Schoenbohm To: topband@contesting.com Sent: Tuesday, November 8, 2016 5:12 PM Subject: Re: Topband: 160 m inverted L Bread slicers have their issues and are not really the best solution. Herb, I must agree with you. Over 25 years ago, I tried to shunt feed my tower. I had a very heavy duty "bread-slicer".It tuned fine. But when I put power, 1500 watts, to it the plates warped. I changed to a couple of Vacuum Variables, 500pF @ 7.5kV and everything is fine. The tuning has never changed. I set it to 1830kHz @ 1:1 vswr and the 2:1 bandwidth is ~ 40kHz. 73 de Price W0RI _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Bread slicers have their issues and are not really the best solution. Using a fixed high current mica G2 broadcast capacitor of a higher value than you need, and making it variable with a series inductor is the way to go. This is what broadcast stations do in their ATU's. I haven't ever seen a bread slicer in a radio station ATU. A good high current mica cap and a flat wound taped coil IMHO is the way to make everything work well with no breakdowns. For a wide range of matching consider a bridge T with fixed components and taped coils. Go to W8JI's wonderful site for the values you need based on the impedance presented to your feed-line. Herb, KV4FZ On 11/8/2016 6:55 PM, Rob Atkinson wrote: A vacuum variable for L impedance matching is unnecessary. Vacuum variable capacitors leak eventually. It take a long time for them to go through their ranges and you have to have the mechanics outside if you perform remote tuning, to sense or count turns to track when the v.v. is nearing its maximum or minimum. It is far far easier and faster to use an air variable that rotates freely. You only need to keep it sheltered. Elevated radials are fine provided they are high enough to be decoupled from earth, which for most hams is difficult to accomplish on 160 m. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
A vacuum variable for L impedance matching is unnecessary. Vacuum variable capacitors leak eventually. It take a long time for them to go through their ranges and you have to have the mechanics outside if you perform remote tuning, to sense or count turns to track when the v.v. is nearing its maximum or minimum. It is far far easier and faster to use an air variable that rotates freely. You only need to keep it sheltered. Elevated radials are fine provided they are high enough to be decoupled from earth, which for most hams is difficult to accomplish on 160 m. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
On Tue, Nov 8, 2016 at 12:23 PM, Rob Atkinson wrote: > I have no idea what a "FCP" is, but it doesn't matter. > > 1. An inverted L is an _unbalanced_ antenna. Therefore you don't need a > balun. > An FCP is a Folded Counterpoise. Basically, it's an elevated radial for 160m ops without room for a proper radial system. http://lists.contesting.com/_topband/2012-07/msg00413.html And we can use FAR fewer radials if we elevate them. lists.contesting.com/_topband/2007-11/msg00248.html And elevated radials require a good common-mode choke. This page links to what I used, though K9YC's design called for another core and another turn or two. www.w0btu.com/160_meters.html#inv-l_antenna 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
I have no idea what a "FCP" is, but it doesn't matter. 1. An inverted L is an _unbalanced_ antenna. Therefore you don't need a balun. 2. This means you can feed it with unbalanced line, i.e. coax. 3. You can use an unbalanced matching network such as an L network, preferably at the feedpoint. 4. Make the total length of the driven element around 140 feet and put down enough radials, 60 to 100 is good, and you have no problems with common mode RF on the feedline. The returning current to the feedpoint is distributed over enough conductors so that what's on the feedline is minuscule. If you have to fool around with ferrite cores and such then you don't have enough radials down. 73 Rob K5UJ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
FWIW mine is cut by trial and error to 1825 and is approximately 65 feet vertical and 80 feet horizontal. I have moved it around to three different locations over the last 2 years. The dimensions change very little, perhaps 2 feet. The SWR can be tweaked by raising or lowering the FCP a little. Good luck John G3XHZ Sent from my iPhone > On 8 Nov 2016, at 03:23, Wes Attaway (N5WA) wrote: > > I haven't run any numbers but it seems like you should just shorten the > horizontal wire (resonance freq is too low). I would go back to about 65' > horizontal. Somewhere in the range of 60' to 70' you should get close > enough. > > --- > Wes Attaway (N5WA) > (318) 393-3289 - Shreveport, LA > Computer/Cellphone Forensics > AttawayForensics.com > --- > > -Original Message- > From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Art Heft > Sent: Monday, November 07, 2016 3:06 PM > To: topband@contesting.com > Subject: Topband: 160 m inverted L > > I finally got the inverted L up this afternoon. Vertical dimension is 65' > and the almost horizontal dimension is 95'. I am using a very carefully > built FCP and the commercial transformer. My SARK 110 shows resonance at > about 1.68 MHz but the resistive part is up around 1000 ohms. Taken right > at the antenna. Doesn't seem right to me. Any ideas? > 73, Art K8CIT Hillman MI > _ > Topband Reflector Archives - http://www.contesting.com/_topband > > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Hi Wes, The issue here is that he is not over resonant radials and a balun which would likely call for what you suggest. He's over an FCP roughly 130 ohms capacitive reactance and a true transformer which has normal residual inductance. Horizontal plus vertical from 140' to 155' is common for L/FCP cut for R=50 and X=whatever often corrected by a series cap. This extra length has the performance advantage of improving RF current density up high on the vertical wire. When an L and counterpoise are very efficient the ground characteristics and surroundings can "pull" the particulars. That is why the sweet length is a range instead of a singular value. 73, Guy K2AV On Monday, November 7, 2016, Wes Attaway (N5WA) wrote: > I haven't run any numbers but it seems like you should just shorten the > horizontal wire (resonance freq is too low). I would go back to about 65' > horizontal. Somewhere in the range of 60' to 70' you should get close > enough. > >--- > Wes Attaway (N5WA) > (318) 393-3289 - Shreveport, LA > Computer/Cellphone Forensics > AttawayForensics.com >--- > > -Original Message- > From: Topband [mailto:topband-boun...@contesting.com ] On > Behalf Of Art Heft > Sent: Monday, November 07, 2016 3:06 PM > To: topband@contesting.com > Subject: Topband: 160 m inverted L > > I finally got the inverted L up this afternoon. Vertical dimension is 65' > and the almost horizontal dimension is 95'. I am using a very carefully > built FCP and the commercial transformer. My SARK 110 shows resonance at > about 1.68 MHz but the resistive part is up around 1000 ohms. Taken right > at the antenna. Doesn't seem right to me. Any ideas? > 73, Art K8CIT Hillman MI > _ > Topband Reflector Archives - http://www.contesting.com/_topband > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > -- Sent via Gmail Mobile on my iPhone _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
I haven't run any numbers but it seems like you should just shorten the horizontal wire (resonance freq is too low). I would go back to about 65' horizontal. Somewhere in the range of 60' to 70' you should get close enough. --- Wes Attaway (N5WA) (318) 393-3289 - Shreveport, LA Computer/Cellphone Forensics AttawayForensics.com --- -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Art Heft Sent: Monday, November 07, 2016 3:06 PM To: topband@contesting.com Subject: Topband: 160 m inverted L I finally got the inverted L up this afternoon. Vertical dimension is 65' and the almost horizontal dimension is 95'. I am using a very carefully built FCP and the commercial transformer. My SARK 110 shows resonance at about 1.68 MHz but the resistive part is up around 1000 ohms. Taken right at the antenna. Doesn't seem right to me. Any ideas? 73, Art K8CIT Hillman MI _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 m inverted L
Hi Art, Don't know whether you are measuring L to FCP with nothing else connected or measuring shack side of isolation transformer. You should be measuring on shack side of transformer, with L and FCP connected. A feed R of 1000 sounds way, way far off. A feed R of 40-50-60-70-80 would be expected depending on the ground underneath and close dielectric material. But R=1000 is way out of range. You need to get that figured out before you go any further. I have also found that without telling me, some have been measuring in the shack something like 50-100 feet of coax out to the transformer and L/FCP. The impedance transformations of isolation transformer and quarter-wave-ish coax run is like doing all your driving in reverse looking through the rear view mirror. CAN be done, but you have to understand all the ugly, backward and confusing aspects of pruning the far end of an antenna looking through all that stuff. Make sure on the transformer, with nothing connected to it, that the FCP/L connections show a short between them, and the coax side SO239 shell to center conductor shows a short, and that L to coax center conductor is an open. It is possible that end of the bifilar winding can get flipped (very rare on a commercial model, but does happen and very confusing until rectified). Your vert+horiz=160 is a little longer horizontal start point than typical. 1.68 MHz for outright resonance of wires of your dimensions by themselves is not out of bounds. The instructions for simple tuning of an L/FCP is to make vertical plus horizontal 155-160 feet, and then remove a foot or 6 inches at a time from the far end of horizontal, watching the nature of the change carefully each time, until things get moderate at the coax side of the transformer. Do **not** get in a hurry in this process. Record your sweep image with the length at each check. Don't try to calculate the end from the change as if it was linear, and make a giant leap. In experience, it is not generally linear. Will be happy to get with you over the phone if you think that would help. Let me know and I'll pass along my cell number. 73, Guy K2AV On Mon, Nov 7, 2016 at 4:05 PM, Art Heft wrote: > I finally got the inverted L up this afternoon. Vertical dimension is 65' > and the almost horizontal dimension is 95'. I am using a very carefully > built FCP and the commercial transformer. My SARK 110 shows resonance at > about 1.68 MHz but the resistive part is up around 1000 ohms. Taken right > at the antenna. Doesn't seem right to me. Any ideas? > 73, Art K8CIT Hillman MI > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160 m inverted L
I finally got the inverted L up this afternoon. Vertical dimension is 65' and the almost horizontal dimension is 95'. I am using a very carefully built FCP and the commercial transformer. My SARK 110 shows resonance at about 1.68 MHz but the resistive part is up around 1000 ohms. Taken right at the antenna. Doesn't seem right to me. Any ideas? 73, Art K8CIT Hillman MI _ Topband Reflector Archives - http://www.contesting.com/_topband
