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1. Re: Topband: K8UR array (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Sun, 07 Dec 2003 02:02:29 -0500
One should always assume that a balun is needed, unless there is a positive proof to the contrary, such as coax being positioned behind an infinite conductive plane, etc. Published antenna designs [a
/archives//html/Topband/2003-12/msg00036.html (7,360 bytes)

2. Topband: "Magnetic" loops vs. pseudo-Brewster angle (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 10 Dec 2003 07:45:32 -0500
ON4UN's "Low Band DXing", 3rd Edition On page 7-54, picture 7-71 is titled "Vertical and horizontal radiation pattern of a small magnetic loop erected in a plane perpendicular to the ground (classic
/archives//html/Topband/2003-12/msg00090.html (6,986 bytes)

3. Re: Topband: Non-inductive resistors (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 18 Dec 2003 20:15:34 -0500
In the 500 Ohm range at 1.8 MHz resistor inductance is generally not a problem (except with wirewound). To get only 1 Ohm of reactance takes 88 nH of inductance. Most general-purpose resistors are we
/archives//html/Topband/2003-12/msg00149.html (8,133 bytes)

4. Topband: 160 Meter BALUNS (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Mon, 22 Dec 2003 17:53:13 -0500
[This message is repeated because it didn't make through few days ago.] There are several point one should consider. 1. One doesn't have to prove that an antenna in question NEEDS a balun. On the con
/archives//html/Topband/2003-12/msg00188.html (10,555 bytes)

5. Re: Topband: To Balun or not to Balun that is the question. (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Tue, 30 Dec 2003 12:23:11 -0500
Feedline radiation is not the only problem caused by omitting baluns, and it is not the most serious one. As you pointed out, it may even be useful at times. However, there are other problems which m
/archives//html/Topband/2003-12/msg00291.html (9,131 bytes)

6. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 31 Dec 2003 14:34:59 -0500
The trend stops rather quickly and it is easy to have too many turns on higher bands. After parallel resonance is reached impedance drops. Baluns and other chokes are used in the frequency region wel
/archives//html/Topband/2003-12/msg00335.html (6,563 bytes)

7. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 31 Dec 2003 19:43:04 -0500
A choke should be regarded a short-circuited transmission line, with input [near] end being at choke treminals, and shorted output [far] end being in the middle of the choke. So the [differential] wa
/archives//html/Topband/2004-01/msg00000.html (7,929 bytes)

8. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 31 Dec 2003 20:43:16 -0500
The actual mechanism is that of a transmission line, not of a simple capacitance. topband, the inductor reactance is multiplied by four when doubling the number of turns. My own experience from windi
/archives//html/Topband/2004-01/msg00002.html (10,514 bytes)

9. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 01 Jan 2004 00:10:02 -0500
Hi Mauri, The resonance you are talking about is the series resonance which shows itself as an impedance minimum. Of course, it must be avoided. Below it sits the first parallel resonance, which show
/archives//html/Topband/2004-01/msg00003.html (11,310 bytes)

10. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 01 Jan 2004 00:24:47 -0500
I missed this one on the first reading. The behaviour you described is that of a "lossless uniform transmission line", uniform meaning constant characteristic impedance accross the line length. Howev
/archives//html/Topband/2004-01/msg00004.html (8,427 bytes)

11. Re: Topband: Balun Discussions (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 01 Jan 2004 13:27:48 -0500
Mauri, what you just described is exactly a transmission line :-) No, it is just your beleif, just as it was mine. But making a few sound measurements changes that easily. Sure, if "Under the resonan
/archives//html/Topband/2004-01/msg00015.html (8,132 bytes)

12. Re: Topband: 160m int L (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Mon, 05 Jan 2004 20:58:10 -0500
My first idea would be to try inverted-T instead of inverted-L in order to avoid high angle radiation as much as possible. Even if not set up exactly symmetrical, it may be preferable to inverted-L i
/archives//html/Topband/2004-01/msg00048.html (7,627 bytes)

13. Re: Topband: Apparent Multiple Resonances on a single antenna (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Wed, 07 Jan 2004 01:00:57 -0500
If your antenna is properly fed with a good balun, you'd get resonances on odd harmonics with SWR generally increasing with frequency due to increasing radiation resistance. This implies that both r
/archives//html/Topband/2004-01/msg00073.html (8,157 bytes)

14. Re: Topband: Col-atch-co 160/80 meter antenna (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Fri, 09 Jan 2004 22:48:01 -0500
Didn't try the Col-atch-co antenna, but speaking generally, top coil (plus loading wires) gives better current distribution in the antenna, resulting in higher radiation resistance, lower losses and
/archives//html/Topband/2004-01/msg00111.html (6,728 bytes)

15. Re: Topband: keying waveform-ARRL savy (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Tue, 27 Jan 2004 16:41:50 -0500
Everything is OK with waveforms. Key closure is represented by a low level, and there is a substantial delay to RF output. 73, Sinisa YT1NT, VA3TTN _______________________________________________ Top
/archives//html/Topband/2004-01/msg00279.html (7,413 bytes)

16. Re: Topband: Receivers, Noise Blankers and Key Clicks (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 05 Feb 2004 06:53:17 -0500
On my MkV setting A/B gain to minimum was not enough. This probably depends on individual transistor characteristcs. Safe way is to do the mod. 73, Sinisa YT1NT, VA3TTN ______________________________
/archives//html/Topband/2004-02/msg00061.html (10,018 bytes)

17. Re: Topband: Receivers, Noise Blankers and Key Clicks (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 05 Feb 2004 07:05:49 -0500
How about unit-to-unit variation and measurement uncertainty? Parameters in question are not adjusted/tested/guaranteed by manufacturers, so the values "just happen". 73, Sinisa YT1NT, VA3TTN _______
/archives//html/Topband/2004-02/msg00062.html (9,982 bytes)

18. Re: Topband: dynamic range (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 05 Feb 2004 11:22:08 -0500
It's 50 uV into 50 Ohm load. Unloaded generator has 100 uV. 100uV plus 60dB is 100 mV. It takes 60 dB from 100 uV to 0.1 uV. I dream about it :-) My MkV can be reasonably trusted on 14 MHz from S8 to
/archives//html/Topband/2004-02/msg00074.html (7,824 bytes)

19. Re: Topband: dynamic range (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 05 Feb 2004 16:21:00 -0500
I've even found that S meters do not respond strictly to envelope peak voltage, or envelope average voltage (in the case of speech or other varying signals). Indication can be anywhere from peak to a
/archives//html/Topband/2004-02/msg00087.html (7,617 bytes)

20. Re: Topband: BDR redux (score: 1)
Author: Sinisa Hristov <shristov@ptt.yu>
Date: Thu, 05 Feb 2004 16:38:16 -0500
We've been enjoying "AGC Treshold" for many decades, although we didn't use the name until the recent marketing breakthroughs :-) AGC threshold determines the point above which AGC loop is operationa
/archives//html/Topband/2004-02/msg00088.html (7,803 bytes)

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