Re: Topband: 160M Balun
Hi Frank, I just don´t see a reason to make chokes self resonant. If one really needs that a parallel resonant LC circuit can be formed with a normal choke and a capacitor. On my 160m dipole the choke at the feed point is wound with RG 141 on a stack of two large ferrite toroids which gives me a Z of about 10k. In addition the outer conductor is connected to the tower after a quarter wave length and the coax run inside the tower and grounded to one leg. The same tower is direct fed as an elevated GP at the 25m level against two sloping radials with the outer connector bonded to the tower. I never saw any common mode current when the common mode chokes XL was at least 100 times the coax Z. 73 Peter -Original Message- From: donov...@starpower.net [mailto:donov...@starpower.net] Sent: Freitag, 30. März 2018 19:30 To: topband@contesting.com Subject: Re: Topband: 160M Balun Hi Peter, What you need in a common mode choke is adequate resistive component to absorb common mode signals as heat. The choke doesn't need to be at resonance to achieve adequate choking resistance, but it doesn't hurt either. It takes some thought and technical understanding to determine how much common suppression is enough. And common mode chokes aren't the only way to adequately suppress common mode signals. A low impedance radial system provides good common mode suppression. Grounding the coax feed line to a center-fed dipole 1/4 wavelength or 3/4 wavelengths from the dipole feed point also provides good common mode suppression, certainly more than you ever need for a dipole. This assumes that the feed line runs at approximately 90 degrees from the dipole. Pulling the feed line significantly away from 90 degrees significantly increases common mode. An off-center-fed dipole is much worse because its very difficult to build a choke with adequate power handling capability and good choking performance. You can't understand your needed common mode signal suppression without understanding your signal environment and the directive performance you want to achieve from your antenna. For example: A multi-transmitter or SO2R station needs much more attention to common mode suppression than a single operator low power station A highly directive multi-element Yagi needs much more common mode suppression than a dipole or a vertical. Coax feed lines properly installed and bonded to a tower has less common mode signals than a coax feed line suspended well above the ground. Perhaps the worst case need for common mode suppression is directive receiving antennas with very low signal levels such a small terminated loop (K9AY, Flag, etc) or a small "magnetic" loop. Both require extreme attention to common mode signal suppression, including a strong preference for buried feed lines, control lines and power cables. 73 Frank W3LPL From: "Peter Voelpel" <dj...@t-online.de> To: "Jim Thomson" <jim.t...@telus.net>, topband@contesting.com Sent: Friday, March 30, 2018 4:47:44 PM Subject: Re: Topband: 160M Balun Why do you want it resonant? 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Thomson The 160m CM choke needs to resonate lower in freq. It requires more cores to shift the res freq down. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160M Balun
Hi Peter, What you need in a common mode choke is adequate resistive component to absorb common mode signals as heat. The choke doesn't need to be at resonance to achieve adequate choking resistance, but it doesn't hurt either. It takes some thought and technical understanding to determine how much common suppression is enough. And c ommon mode chokes aren't the only way to adequately suppress common mode signals. A low impedance radial system provides good common mode suppression. Grounding the coax feed line to a center-fed dipole 1/4 wavelength or 3/4 wavelengths from the dipole feed point also provides good common mode suppression, certainly more than you ever need for a dipole. This assumes that the feed line runs at approximately 90 degrees from the dipole. Pulling the feed line significantly away from 90 degrees significantly increases common mode. An off-center-fed dipole is much worse because its very difficult to build a choke with adequate power handling capability and good choking performance. You can't understand your needed common mode signal suppression without understanding your signal environment and the directive performance you want to achieve from your antenna. For example: A multi-transmitter or SO2R station needs much more attention to common mode suppression than a single operator low power station A highly directive multi-element Yagi needs much more common mode suppression than a dipole or a vertical. Coax feed lines properly installed and bonded to a tower has less common mode signals than a coax feed line suspended well above the ground. Perhaps the worst case need for common mode suppression is directive receiving antennas with very low signal levels such a small terminated loop (K9AY, Flag, etc) or a small "magnetic" loop. Both require extreme attention to common mode signal suppression, including a strong preference for buried feed lines, control lines and power cables. 73 Frank W3LPL - Original Message - From: "Peter Voelpel" <dj...@t-online.de> To: "Jim Thomson" <jim.t...@telus.net>, topband@contesting.com Sent: Friday, March 30, 2018 4:47:44 PM Subject: Re: Topband: 160M Balun Why do you want it resonant? 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Thomson The 160m CM choke needs to resonate lower in freq. It requires more cores to shift the res freq down. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160M Balun
One can do better than 7 turns inside FT240 forms if you use RG400 for the winding and terminate the winding PL259's with UG175 adapters for the RG400. Choke made this way are near indestructible except ferrite cores blocking hundreds of volts RF common mode. RG400 is rated 7 kW due to teflon jacket, dielectric and fine silvered copper weave and flexible multistrand center conductor. Requires connectors, but so does any commercial choke, and not all of them use the high quality coax. Soldering RG400 is nice because you can't melt it. The usual sealing procedure for choke to regular coax: tape to cover shells and double female adapter, coax wrap over all that plus half inch either end, tape over coax wrap, scotch liquid tape over tape. If you do it this way, you can measure and test the thing on the bench before you ever take it outside. I've made those with T300A-2 powdered iron cores and a parallel HEC cap in the center and resonated them at 1.9 or 2 MHz for a parallel tuned block where levels to be blocked have heated and destroyed #31's (extreme unfortunate situation). 73, Guy K2AV ** *Lowering SWR does * * not * * predict performance.* *A dummy load, * * with its perfect SWR, * * is a worse antenna * * than a light bulb. * *First discern and remove * * the loss in low band* * antenna systems.* *--* On Fri, Mar 30, 2018 at 12:09 PM, Jim Thomson <jim.t...@telus.net> wrote: > Date: Fri, 30 Mar 2018 07:22:18 -0400 > From: "N2TK, Tony" <tony@verizon.net> > To: <topband@contesting.com> > Subject: Topband: 160M Balun > > balun. > #31 cores with 7 turns of coax would be a better balun. >cores > > <N2TK, Tony > > ## Although 7 turns of 213 sized coax through 5 x type 31 > cores works good > on 160m... aprx 5 k ohms, the choke will resonate on 3 mhz !You > cant get more than > 7 turns of coax through a 2.4 inch OD / 1.4 inch ID core. The 160m > CM choke needs > to resonate lower in freq. It requires more cores to shift the res freq > down. I dont > know how many more, but I suspect 7-12 cores would do the job, and > certainly > be an improvement. You wont blow it up either. > > ## I suspect your current bead balun wont provide very much Z on > 160m..and it > will all be reactive. > > Jim VE7RF > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160M Balun
## Much higher Zand much higher RSand minimal Xs. Plan B would be to use RG-400... but more than 7 turns. ## N3RR has his 160m CM chokes between 16k and 22k ohms. If you are going to build a 160M CM choke, you may as well do it right the 1st time. Jim VE7RF -Original Message- From: Peter Voelpel Sent: Friday, March 30, 2018 9:47 AM To: 'Jim Thomson' ; topband@contesting.com Subject: RE: Topband: 160M Balun Why do you want it resonant? 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Thomson The 160m CM choke needs to resonate lower in freq. It requires more cores to shift the res freq down. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160M Balun
Why do you want it resonant? 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Thomson The 160m CM choke needs to resonate lower in freq. It requires more cores to shift the res freq down. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160M Balun
Hi Jim, Have you considered using RG-303 or RG-400 ? They're commonly available on the internet and at hamfests at discount prices. Its similar in diameter to RG-58 but rated well over 1500 watts on 160 meters. However... You don't need a high performance choke on your vertical unless you have elevated radials or a sparse radial system with few radials or short radials. A good low impedance radial system will provide excellent common mode suppression. 73 Frank W3LPL - Original Message - From: "Tony N2TK" <tony@verizon.net> To: topband@contesting.com Sent: Friday, March 30, 2018 11:22:18 AM Subject: Topband: 160M Balun I shunt feed my tower for Topband. Presently using a Comtek 100 bead balun. After reading K9YC's article on baluns it would seem that a stack of five #31 cores with 7 turns of coax would be a better balun. Would I notice an improvement in any way by switching baluns? If the answer is I would notice an improvement what about using sixteen turns #12 THHN wire on #31 core as shown in K9YC's article? How many cores would I need for 1500W? Tnx for any feedback N2TK, Tony _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160M Balun
Date: Fri, 30 Mar 2018 07:22:18 -0400 From: "N2TK, Tony" <tony@verizon.net> To: <topband@contesting.com> Subject: Topband: 160M Balun http://www.contesting.com/_topband
Re: Topband: 160M Balun
I measured the Comtek bead balun on 160m and found there is low choking resistance. I use the K9YC design with good results, whether it will make any difference in your antenna system is something you will need to try. With more than 5x the choking resistance with the K9YC 7T on 5 #31core you may see a reduction in noise and feedline involvement. I use RG400 or RG142 TFE coax which can easily handle QRO on 160m and fits in a 4 x 4 x 4 PVC junction box. I haven't made any of the bifilar THHN designs. Grant KZ1W On 3/30/2018 4:22 AM, N2TK, Tony wrote: I shunt feed my tower for Topband. Presently using a Comtek 100 bead balun. After reading K9YC's article on baluns it would seem that a stack of five #31 cores with 7 turns of coax would be a better balun. Would I notice an improvement in any way by switching baluns? If the answer is I would notice an improvement what about using sixteen turns #12 THHN wire on #31 core as shown in K9YC's article? How many cores would I need for 1500W? Tnx for any feedback N2TK, Tony _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160M Balun
I shunt feed my tower for Topband. Presently using a Comtek 100 bead balun. After reading K9YC's article on baluns it would seem that a stack of five #31 cores with 7 turns of coax would be a better balun. Would I notice an improvement in any way by switching baluns? If the answer is I would notice an improvement what about using sixteen turns #12 THHN wire on #31 core as shown in K9YC's article? How many cores would I need for 1500W? Tnx for any feedback N2TK, Tony _ Topband Reflector Archives - http://www.contesting.com/_topband
