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141. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 12:57:25 -0400; Let's do some quick math.... 234/1.82=128.57 gives us the length in feet of a quarter wave at 1.820 mHz. That's not correct. The number is 245.8926/F, which is rounded to 246/F. A quarter wave in fre; /archives//html/Topband/2012-09/msg00038.html (8,239 bytes)
142. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 13:44:15 -0400; I think the big error, using 234 instead of ~246, is pretty important to everyone. That math is a bit too simple, because Vf VARIES as function of frequency. The PUBLISHED Vf is for VHF, but the Vf i; /archives//html/Topband/2012-09/msg00039.html (11,375 bytes)
143. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 17:24:24 -0400; Likewise, Zo is only sqrt (L/C) at VHF. The more complete equation is sqrt [ (R+J omega L) /( G + J omega C) ] At VHF, the equation SIMPLIFIES to sqrt (L/C) At low audio frequencies, and up to VHF, G; /archives//html/Topband/2012-09/msg00043.html (12,872 bytes)
144. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 21:28:46 -0400; Run the numbers and for RG-6 we see that sq root of L/C is good above a couple hundred kHz. Dave WX7G I just ran it in MathCAD and it showed a Zo and Vf slope starting down around 150 kHz, but I assu; /archives//html/Topband/2012-09/msg00048.html (9,464 bytes)
145. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 11 Sep 2012 04:28:34 -0400; Tom .... I think everything is real quiet while a bunch of folks are busy looking at manuals and crunching numbers with their analyzers. Wes, The problem Jim suggests is real, but the numbers are so; /archives//html/Topband/2012-09/msg00052.html (11,776 bytes)
146. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 11 Sep 2012 10:20:00 -0400; Some flooded foam-core F-6 starts to show what could be problematic velocity factor changes, for critical phased arrays, below 1 MHz. Above 1 MHz any change is lost in either measurement errors or ca; /archives//html/Topband/2012-09/msg00057.html (9,101 bytes)
147. Re: Topband: RX epiphany? (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 07:38:59 -0400; Hi well I've only been QRV since June here but the QRN level seems noticeably worse than my previous QTH in the W6 desert even though my current QTH is also quiet, limited by only propagated QRN. >>>; /archives//html/Topband/2012-09/msg00069.html (10,536 bytes)
148. Re: Topband: Pulse noise source help! (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 10:05:34 -0400; I have had a longstanding problem with pulse noise off my SW BOG. The pulses are ~5khz wide, ~1 to 1.5 S units in amplitude, are spaced every 12 khz, do not drift (one always right on 1825!), and ext; /archives//html/Topband/2012-09/msg00071.html (8,086 bytes)
149. Re: Topband: Radials over a stone wall (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 11:27:06 -0400; Thanks for all the feedback on how to get the radials over/under/through the wall. After playing with this for the past few weeks I realize no way to go under as test poundings on rods indicates the; /archives//html/Topband/2012-09/msg00073.html (8,567 bytes)
150. Re: Topband: RX epiphany? (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 11:37:20 -0400; I agree with Tom's assessment. I wouldn't be too quick to give up on your tx 4 square. Having a tx 4 square, a 1/4 wave vertical, and an 8 circle rx array, I find the 4 square really does hear quite; /archives//html/Topband/2012-09/msg00074.html (9,034 bytes)
151. Re: Topband: RX epiphany? (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 13:08:07 -0400; In your opinion; given a receive antenna with negative gain, at what level does the negative gain start to come into play? -25 dBi, -35 dBI ? There are several variables to this. Estimating from a mo; /archives//html/Topband/2012-09/msg00076.html (9,148 bytes)
152. Re: Topband: Radials over a stone wall (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 13 Sep 2012 13:49:33 -0400; Thanks for the info. This is what I was looking for - info from someone who has modeled the radials and/or actual experience with measurements. Going over the wall simplifies things for me both for t; /archives//html/Topband/2012-09/msg00078.html (8,773 bytes)
153. Re: Topband: RX epiphany? (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 14 Sep 2012 21:09:52 -0400; Hi thanks to all for the replies. Sorry I wasn't clear my QTH is northern Thailand. The point I was trying to make is that even though it is a noisy part of the season it is apparently less noisy at; /archives//html/Topband/2012-09/msg00088.html (10,571 bytes)
154. Re: Topband: The use of digital modes on 160 metres (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 03:25:01 -0400; While there may be many that disagree with me I love digital modes on 160. I primarily use JT65 and it has been one of the reasons that I have worked Japan and New Zealand on TB. I use it primarily w; /archives//html/Topband/2012-09/msg00097.html (14,088 bytes)
155. Topband: Old Radios (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 12:47:01 -0400; Specifically, every year The Antique Wireless Association (NY, USA) sponsors the "Bruce Kelley 1929 QSO Party" for two weekends in late autumn: this year marks the first time that 160-meters will be; /archives//html/Topband/2012-09/msg00100.html (9,058 bytes)
156. Re: Topband: The use of digital modes on 160 metres (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 14:20:52 -0400; Ever listen on Top Band during a contest? On a CW weekend, CW goes from 1800 to at least 1910 kHz, and on a SSB weekend SSB extends well below 1825 kHz. A temporary operation during a few special eve; /archives//html/Topband/2012-09/msg00104.html (14,048 bytes)
157. Re: Topband: Topband Digest, Vol 117, Issue 20 (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 14:53:38 -0400; An additional issue for weak sig CW folks is the nature of digi operations. Digi operators don't always check for pre-existing activity. The result is the digi setup begins its 1 minute of howling, i; /archives//html/Topband/2012-09/msg00106.html (8,797 bytes)
158. Re: Topband: Topband Digest, Vol 117, Issue 20 (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 18:14:50 -0400; Tom, "on point" ....... I am, almost exclusively, a CW and Digi op in that order. I will say, anecdotally, that I have not experienced any interference caused by one or the other to the other on 160.; /archives//html/Topband/2012-09/msg00112.html (13,658 bytes)
159. Topband: Digimodes (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 16 Sep 2012 20:28:55 -0400; Tom, all you have to do is open you filter up to say 1800 hz or maybe a little more, then sit and watch how many signals you can decode on a busy 20 meter psk31 day. I regularly copy signals that are; /archives//html/Topband/2012-09/msg00117.html (12,525 bytes)
160. Re: Topband: TB digital (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 17 Sep 2012 07:33:03 -0400; I'm not surprised some of us don't know the band or history of use, or have not read IARU bandplans. What I wish we could do, is be a little nicer to each other as we learn things from each other. Wh; /archives//html/Topband/2012-09/msg00129.html (11,700 bytes)

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