Topband: identifying noise source
GM, I recently have some strange, pulsating noise on all 300 deg / NA beverages. Maybe someone have already experienced anything like this - what kind of device it can be? Here is a recording on wide filters in AM, around 3,4MHz (maximum signal). https://drive.google.com/file/d/1zTWirLyNiD2aYd7oJQjt8HhG9rgttcvn/view It's starts late in the evenings and can be heard till 8-9:00 AM. In daylight it gets stronger. I actually have 2 different RX arrays for NA, the distance is abt 300m from each other, but the noise is abt the same level on both antennas. I guess it means the source can be even few km's away? 73 Mac SP2XF/ SN2M _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: RX antenna switching - unused ports
Hi Brad, what I can say from my perspective - in the last 10 years I have tried both grounding and terminating through 75ohm resistor. With the terminating I see absolutely no pattern distortion on my Beverage's, which was not so obvious when direct grounding was used. My Bev's often are crossed 45 deg, height is 1,8-2,0m. I use only isolated transformers / separate windings. 73's Mac SP2XF / SN2M - Original Message - From: "Brad Denison" To: Sent: Thursday, June 08, 2017 1:54 PM Subject: Topband: RX antenna switching - unused ports All, I am working a homebrew RX antenna switch box for my beverages, flags and shared apex loop array and am looking for design advice. Can someone educate me on the proper way to handle unused ports: 1) Leave all unused ports open 2) Ground all unused ports 3) Terminate unused ports to 75 ohm I have seen various commercially available switch boxes with all of these configurations but it is not clear to me if any of these variations are best, i.e does it matter? Thanks, Brad, W1NT _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 vertical/L
Hi , did anyone try to match such 160m vertical /L or /T on 80m? How about efficiency? After my 31m tall vertical broke last sunday (now it's 23m only) my idea is to add 2 x15m top loading wires, making a T-vertical. 160m is a priority in this case and I know it will work OK, but I'd like to use it also on 80m. TNX 73's Mac SP2XF / SN2M - Original Message - From: To: "topband" Sent: Wednesday, November 30, 2016 2:16 PM Subject: Re: Topband: 160 vertical/L Hi Mike, An inverted-L with 50-60 feet vertical is a far superior choice than a bottom loaded vertical. Its much more efficient, its bandwidth is much broader and you don't have to deal with the very high voltages at the base of the loaded vertical, especially if you're running high power. 73 Frank W3LPL - Original Message - From: "Don Kirk" To: "W0MU Mike Fatchett" Cc: "topband" Sent: Wednesday, November 30, 2016 12:32:26 PM Subject: Re: Topband: 160 vertical/L HI Mike, I use a 68 foot based loaded vertical on 160 meters with 55 short buried ground radials (2500 feet of ground radials). I only run 100 watts and located near Indianapolis. I would prefer an Inverted-L over the base loaded vertical on 160 meters (the L would be much more efficient), but having said that I did acquire my 160 meter DXCC last year (all CW) and most of the contacts were during years when 160 meters was in very poor condition. Note: I do use small pennant antennas for RX on 160 meters. For starters it sure would be easy to temporarily install a base loading coil to test out your full size 80 meter vertical on 160 meters versus your 33 foot vertical. You can use part of the loading coil you install on the full size 80 meter vertical with a fixed high voltage silver mica cap to form a simple L network (that's what I do and it works great). This would allow you to easily compare your two TX antennas. Note: neither end of my base loading coil is connected to ground (my base loading coil is between the bottom of my 68 foot vertical and the center conductor of my feedline. I use an MFJ 404-0669 air wound coil as my loading coil / L network. But if you can install an Inverted-L easily, than I would skip what I have said above and just install the Inverted-L. Don (wd8dsb) On Wed, Nov 30, 2016 at 1:33 AM, W0MU Mike Fatchett wrote: I have a full sized 80m vertical and a Top loaded Cushcraft 33ft vertical for 160. The Cushcraft gets out but not great. I was thinking about using an inverted L over the radial field that I use for the 160. It is 30ish radials of various lengths or I have seen where people have loaded the 80m vertical on 160. I think I recall people are not overly excited about bottom loading the 80. The 80 is unguyed so the top cannot support anything. I can get the vertical part of the L up 50-60 feet. Any feelings one way or another? I can make a switching system for the 80 vert if people think this is a reasonable transmitting solution. I have a rcv array, so I am hoping to improve my xmit signal. W0MU _ 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: Bandpass filters for receive antennas / LW 225khz rejecting
GM All, Can someone recomend me a simple high pass filter that will reject strong AM signal trasmitted at 225 khz? I've just looked at Petr OK1RR website and there is nice filter, but rejects 400khz-1600khz band, so will not work in my case... This signal at 225 Khz comes from Polish Radio I AM station, located abt 120kms away, but it puts 9+60db with ATT-30db turned on (IC 765) and it's quite spourius since abt 3 years (I know they changed something in the audio to make it "more readable"...). In practice, I have QRM and harmonics on 160m (specially in daylight) and it makes impossible measuring any beverage antenna in my QTH, using MFJ or VNA analysers as you can see on this video: https://www.youtube.com/watch?v=pEWTYrRPgjo TNX for help and CU soon on the band 73's Mac SP2XF (SN2M) - Original Message - From: "Tom W8JI" To: Sent: Monday, August 31, 2015 8:43 PM Subject: Re: Topband: Bandpass filters for receive antennas Bandpass filters do nothing for in-band signals -- their only function is to reject OUT OF BAND signals. The primary reason for using bandpass filters IS for RX. A good 160M bandpass filter would be effective at reducing overload from AM broadcast stations. So would a high pass filter. There is a survey of bandpass filters for contesting at this link. http://k9yc.com/BandpassFilterSurvey.pdf I use a high pass filter for rejection of the AM BCB band. Between 70 and 80% of the net power (or voltage) into my RX system comes from distant AM BCB signals. Without a small 5-pole highpass that starts to roll off at 1700 kHz, I can connect a miniature 12V 50 mA incandescent lamp (like the MFJ 1025 uses as a fuse) and it illuminates a dull red. This is with no attempt at matching power to the filament cold resistance. My system can be bothered by the sum of all those thousands of signals, I add a BCB high pass, and then I can run 1500 watts and not bother my own RX when transmitting on 80 or 40 while receiving on 160. Of course I have 500-2000 ft separation on antennas, but this still shows how a bunch of small signals can add up to disaster if they hit something non-linear before being filtered. Always remember there are two problems. One is the absolute limit of in-band signal a receiver system can take. The other is the absolute limit of the sum of all the signals entering an overload sensitive point in the system. Less than one volt peak line voltage is not enough headroom to prevent IM products in a reasonably good system. Back-to-back parallel diodes are fine for Sky Buddy receivers and FT101's. A single diode opposing another diode in parallel will clamp at about 6 dBm if your receiver looks like 75 ohms. Almost all receivers will conservatively take 15-20 dBm, or 2-4 volts peak, at the antenna port in band. If you have a good system, you'll want something other than back-to-back diodes. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BEVS ON SAME SUPPORT
Hi Bill, I have no experience with crossing beverage's but I remember from ON4UN's book the the coupling is marginal in this case and should not affect performance... Maybe there is another problem: I don't think grounding unused bevs is the best solution, I would rather left them "floating" or load with 50ohm (or 75ohm) resistor (which worked best at my QTH). Regarding two opposite directions on the same poles, with some "vertical" spacing - I am also very interested if someone have tested exactely this kind of solution and what were the results. Here, I was going to try it for JA/PY directions in the next season. Well, I always thought it's better solution than standart "two wire beverege", with reflection xfmr, etc. Actually, I don't understand the reason why two close spaced parallel wires in horizontal are OK, and one below another, with reasonable spacing might cause problems (obviously, I consider that the feed point of the opposite direction should be at some distance from the far end of the "main" direction and vice versa). But maybe I'm missing sth and someone with greater knowledge could explain this. here... In September I will share here results of my tests as well. Best 73's from Poland Mac SP2XF - Original Message - From: "Bill and Liz" To: Sent: Wednesday, May 23, 2012 1:36 PM Subject: Topband: BEVS ON SAME SUPPORT > Like ZL3IX, I also had very poor results with a Beverage travelling too > close to a fence. F/B was bad but even worse was coupling of noise picked > up by the fence. > > WRT a second Bev on the same post, 12"-18" is far too close to space the > two wires. I have several Bevs which cross at something other than 90 > degrees and these antennas always seem to be less effective than those > which do not cross another antenna. Even though unused Bevs are grounded, > are not parallell and the crossings are seperated by a foot or more, there > IS coupling which is reflected in slightly elevated noise and lower F/B. > > So, my suggestion regarding running Bevs in opposite directions on the > same poles would be "don't try it"! > > Bill VE3CSK > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: IC 775 clicks
GM/GE, Has anyone ever seen any mod for IC 775 DSP, for getting rid of CW clicks? I mean, kind of solution that they have for FT 1000 Mark V..? BTW, maybe I have a problem with my radio, with the signal S 9+30db on 160m (no amplifier) a friend located 30kms away was hearing my clicks for almost 1,5khz up/dwn, with 400hz filter I'm preparing for the CQWW 160m contest, so yesterday we made several tests and after puting the same power from IC 765 the difference is huge, almost no clicks and nothing detected if we go +/- 0,5 khz from the TX frequency... 73's Mac SP2XF ___ UR RST IS ... ... ..9 QSB QSB - hw? BK