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How long and what type of coax?
Any length will do... 50 ohm coax. |
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snip Oh I see those shiny loading coils must really increase the gain of the antenna huh. I never explained why one antenna outperforms another. I just posted the numbers. You can draw your own explanation. The coil antenna is very ugly. I would opt for a antenna with slightly less antenna gain but with a more pleasant gain for the eyes. Ultimate antenna gain isn't everything. |
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snip
P.S. A 1/4 wave whip of thicker more conductive material can't be beat by a shorter antenna, but my comment was about the common 102" SS whip. Using Mmana to simulate antennas; The difference between a 5' and a 8' copper antenna is 0.3 dB The difference between a 8' copper and 8' stainless steel antenna is 0.6 dB (by the book) a 5' copper antenna will beat a 8' stainless antenna. You hit the nail on the head. Many/most just assume that a 1/4 wave antenna will beat a shorter antenna. They look no further. They read the theory and take the theory as the way things work in the real world. Simple theory isn't always realized in the real world. A quarter wave will only beat a shorter antenna if all the antenna variables are the same except for the length. In the real world our 1/4 wave antenna is a thin SS whip. It can not beat a inch thick 1/4 wave copper antenna. It can't even beat some properly designed 5 foot antennas. |
In , wrote:
snip This may shock and dismay some people, but I agree with you Frank. A 102" stainless steel (or fiberglass) whip properly mounted will beat shortened and loaded antennas any day. Best location would be dead center on the roof, but with a cab-over camper you can't do that permanently, although you could use a mag-mount antenna and place it on top of the camper when you have it onboard. snip A repost of a ACTUAL test: Your test doesn't mean crap, and I'll tell you why. For starters, your -first- test (that you failed to mention) using -two- receivers came up with inconsistent results for five different antennas tested on the transmitter: Tentec: F, 3.1 s units E, 3.05 A, 3 B, 2.85 D, 2.7 C, 2.65 Kenwood: F, 2.3 s units E&B tied at 2.2 D-C tied at 2.15 A, 2.1 This tells me that something is -definately- wrong with your testing procedure. The conditions of this test follow: 1. All connected to Hustler Quick disconnects That could be an issue if one or more of the connectors were not clean, assuming they didn't use the same connector; 2. All used at 1.5 : 1 match or better The match for each antenna was not listed, and I can only assume that they were different. Regardless, what was the forward power with each antenna, and why was that not listed? 3. All tested with a constant tone, constant power transmitter Using....? An audio signal generator and a TRC-453? Was the radio modded? What was the modulation percentage? 4. All used on a three magnet mount on the roof of a truck Now there's a BIG problem -- improper grounding! 5. All tested from a parked vehicle that never moved during each test How did the radio get power? Cigarette lighter? Six feet of 00-guage superflex? Was the engine running? If not, was the battery voltage checked before and after the tests? 6. All tested within a very brief time period of each other (15 sec.) Save for the all-too-uncommon microburst, how is that significant? 7. All used a stationary Kenwood 940 receiver. Why didn't you use two receivers for the second test? 8. The 940 used a vertical beam free and clear of obstacles. Beam, schmeam. What was the resonant frequency of the antenna for the receiver? What kind of match was on the receiver? Were all antennas tuned and tested on the same freq? 9. A video camera and a 31" television was used to display a (31" S- METER) and record the results. Thirteen mile free and clear of obstacles. At 13 miles, another issue you will have is radiation angle. I don't suppose you measured that either, did you? Do you know why that is important? Because you don't state the HAAT of the antenna for either the transmitter or the receiver, nor do you state whether the 13/24 miles was flat. If you just wanted to get a relative signal strength reading without the confound of HAAT, why did you stroll 13 miles instead of only half a mile or so? All you needed to do was clear the near-field, which most engineers consider to be six wavelengths for HF (or 66 meters, a far cry from 13 miles where a lot can happen inbetween). There are WAY too many issues with your test, and any or all of them could have been a factor in your inconsistent readings. Looking back an those threads, it appears that you already knew that, too. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
In , wrote:
On Mon, 20 Oct 2003 18:53:01 -0700, Frank Gilliland wrote: In , wrote: snip At 27 MHz, any antenna shorter then 5 feet is a waste of time. snip Not true. There are antennas at five feet that will match or even surpass a 102" SS whip. Bull****. This has been shown before. Get off your fat ass and do an actual test. You will find that a Stainless Steel 102" whip can be marginally beat. You can not realize this by reading a book! Get off your ass. My "fat ass" has done this test more than once, more than twice.... If, in fact, you do a PROPER test, eliminating ALL reasonable confounds and recording ALL the data, you WILL find that the 9 foot whip just can't be beat, as my "fat ass" has proven more than a DOZEN times before while teaching students how to map an antenna field (which, BTW, was a lab demo for a number of different issues, not just antenna types and field strength measurements). P.S. A 1/4 wave whip of thicker more conductive material can't be beat by a shorter antenna, but my comment was about the common 102" SS whip. Here's your assignment for tomorrow, Tnom: Compare the resistive losses due to skin effect for a 1/4 wave vertical (27 MHz) made of both stainless steel and solid silver wire of the same diameter. And I'm going to help you out by reminding you to integrate the current distribution on the antenna, and I'll even let you pick an arbitrary diameter and disregard the taper. Show your work (and don't skip steps). -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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