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21. Re: Topband: Modeling "Ground" and losses (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 25 Feb 2015 14:39:44 +0100
Their Fig. 7 shows results of simplified (manual) calculations, not measurement results. 73, Sinisa YT1NT, VE3EA _________________ Topband Reflector Archives - http://www.contesting.com/_topband
/archives//html/Topband/2015-02/msg00615.html (7,731 bytes)

22. Re: Topband: Modeling "Ground" and losses (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 25 Feb 2015 15:34:30 +0100
That quote does not apply to Fig. 7, which is 10 pages earlier. This quote from p. 760 applies to Fig. 7: "...the following calculations are made on this basis. The current in the wires is shown...
/archives//html/Topband/2015-02/msg00617.html (8,444 bytes)

23. Re: Topband: vertical balun (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Sat, 30 May 2015 06:40:14 +0200
You should get quite a reasonable SWR with no matching at all. A good high-impedance common mode choke is recommended. 73, Sinisa YT1NT, VE3EA _________________ Topband Reflector Archives - http://ww
/archives//html/Topband/2015-05/msg00044.html (6,592 bytes)

24. Re: Topband: Commond mode choke for Beverage (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Mon, 12 Oct 2015 15:53:56 +0200
If you must use FT240-61, then in a single layer about 18 turns of RG58 would fit, which should give you ~600 Ohms on 1.8 MHz. That would be very good for a dipole, but for a Beverage a much higher i
/archives//html/Topband/2015-10/msg00065.html (9,241 bytes)

25. Re: Topband: Commond mode choke for Beverage (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Mon, 12 Oct 2015 16:03:42 +0200
With 5943003801 and RG58, closely fill-in a single layer, leaving 10-15 mm on the outside perimeter unused. That should be ~16 turns, giving you impedance near 4000 Ohm. Such a choke should be placed
/archives//html/Topband/2015-10/msg00066.html (10,481 bytes)

26. Re: Topband: Commond mode choke for Beverage (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Mon, 12 Oct 2015 20:56:53 +0200
This is exactly as expected. In the first case you fed all the RF received by the outer surface of the coax directly inside the coax, and directly to your RX input. In the second case, a significant
/archives//html/Topband/2015-10/msg00077.html (9,423 bytes)

27. Re: Topband: ADC Overload from MW transmitters (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Tue, 20 Oct 2015 04:01:09 +0200
... A higher sample rate alone will not change the probability of overloading the ADC. The percentage of meaningless samples will stay the same, and consequences of overloading will not change. A hig
/archives//html/Topband/2015-10/msg00140.html (8,822 bytes)

28. Re: Topband: Placement of RX feedline chokes (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 03 Feb 2016 20:02:51 +0100
At each point where the common to differential mode conversion is likely to happen. In other words, where the current on the outside of coax shield is likely to get inside coax. Primary target points
/archives//html/Topband/2016-02/msg00029.html (7,399 bytes)

29. Re: Topband: WEB address correction: : RDF in the real-world (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Fri, 04 Mar 2016 19:28:46 +0100
Because the BOG is "trying" to develop signal voltage between the wire and the earth it sits upon This is misleading at best. The voltage results from the current flowing in the BOG wire. The voltage
/archives//html/Topband/2016-03/msg00071.html (8,029 bytes)

30. Re: Topband: WEB address correction: : RDF in the real-world (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Fri, 04 Mar 2016 19:55:52 +0100
BOG is a traveling wave (Beverage) antenna at its best. If some "tunning" artefacts were present, they probably resulted from incorrect termination, varying height above ground, and varying ground pr
/archives//html/Topband/2016-03/msg00075.html (7,962 bytes)

31. Re: Topband: Handheld Impedance Analyzer (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Tue, 29 Mar 2016 02:23:43 +0200
It would be exactly so if the real part of the antenna input impedance did not change with frequency. The real part of dipole impedance rises quite a bit with frequency, so the resonant frequency as
/archives//html/Topband/2016-03/msg00247.html (9,886 bytes)

32. Re: Topband: The band sans noise (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 20 Apr 2016 17:03:14 +0200
The file starts with some incorrect statements: "All we need is 3 dB SNR for CW and 8 dB for SSB" such a statement is completely meaningless if the measurement bandwidth is not stated "3 dB SNR" with
/archives//html/Topband/2016-04/msg00133.html (7,848 bytes)

33. Re: Topband: FT-1000MP (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 15 Jun 2016 16:19:37 +0200
When you receive on normal (TX) antenna, use: PREAMP=NONE (IPO green LED ON), ATTN=18 dB (max). Whenever the background noise make the S meter move, there is too much gain. 73, Sinisa YT1NT, VE3EA _
/archives//html/Topband/2016-06/msg00067.html (6,555 bytes)

34. Re: Topband: comparison of SNR of two antennas with 2 channel SDR and Linrad (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Sat, 12 Jan 2019 06:58:37 +0100
https://www.youtube.com/watch?v=UzP03mZVLvE Perfectly done and very informative. Thank you, Piotr! 73, Sinisa YT1NT _________________ Searchable Archives: http://www.contesting.com/_topband - Topban
/archives//html/Topband/2019-01/msg00019.html (7,261 bytes)

35. Re: Topband: Fresnel Zone (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Sat, 20 Apr 2019 10:16:37 +0200
This indeed is a classical source, but it should be noted that the derivation assumes that the elevation angle actually used for communication is equal to the elevation angle of the peak of lowest g
/archives//html/Topband/2019-04/msg00101.html (8,363 bytes)

36. Re: Topband: Broadside Beverages and Diversity observations (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Fri, 28 Feb 2020 18:23:03 +0100
In such a case the level of received noise does not depend on antenna directivity. This follows from the fact that all antennas have the same average directivity, i.e. 0 dB 73, Sinisa _______________
/archives//html/Topband/2020-02/msg00256.html (6,923 bytes)

37. Re: Topband: Loop on the ground as a counterpoise (score: 1)
Author: shristov <shristov@ptt.rs>
Date: Wed, 06 May 2020 00:11:42 +0200
The usual kind of field produces radial currents, and that's why we use radial wires. But what kind of field would make the current run in circles? Or is it that the only effective piece of wire is t
/archives//html/Topband/2020-05/msg00019.html (7,344 bytes)


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