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eHam Forums / Misc / RE: Wayne Green W2NSD
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on: Today at 08:32:42 AM
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One ham who has known Wayne for years and who wrote articles for 73, has cautioned people not to confuse Wayne's efforts to sell magazines with his real personal beliefs!  Regardless of the hoopla, I owe Wayne a debt for one editorial he wrote encouraging us to open our minds, embrace those newfangled computers and not be afraid of new modes entering the hobby. He was right! |
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2
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eHam Forums / HomeBrew / RE: Oscillator problem.
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on: Today at 05:37:48 AM
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Obviously you need (better) isolation from the oscillator. Some methods:
-Tube RF
-Follower opamp
-Link coupling (inductive)
-Capacitive
I'm not sure what level of technology you are using. However, you can get ideas from looking at circuits from similar designs. Of course other references like college texts, ARRL/west coast handbooks, Radiotron Designer's Handbook, etc.
Once you look at some references I think the solution will jump out at you! b.
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4
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eHam Forums / Satellites / RE: Will they update SAT status on Amsat.org?
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on: May 22, 2013, 06:33:10 PM
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Appreciate the comments, and the link to the UK version of amsat. To KO4MA, Your two "thoughts" make my point clear. Launching satellites and maintaining interest in satellite operations costs money, and a useful and attractive Website on the "flagship website" would probably go a long way to attracting some of the many new amateur operators entering the hobby. I have donated to the launch funds, but a proper attention to the site would attract new membership. If we acknowledge where the work needs to be done, we can do it. Can anyone here look at the currant Amsat NA site and state that they think we are going to attract the membership and funding to get more satellites launched? I don't think so... I know it is a great deal of work to make a quality website, but if you are trying to obtain hundreds of thousands of dollars in funding, (just like grant writing) you show a "polished" finished proposal. the Amsat page is the "face" we show to new hobbyists AND potential donors.
To reiterate: -If you are an IT security expert, donate your time -If you are not: Send Cash! Yes, the new site is sparse. The problem is that the old site was cobbled together over years and fell to hackers because it was not built to modern security standards. Most of the old satellite information pages are available from the WayBack Machine, using your search engine. 'Satellite Status" IS available at the AMSAT site using User Reports. A different format than we are used to, but perhaps more timely than the old page. Cheers, bill (Fox-1 contributor) |
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5
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eHam Forums / Mods And Repairs / RE: Wouxun KGUV6D V2 HT Flashlight LED Voltage?
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on: May 22, 2013, 06:09:03 PM
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-You are using a $40 radio as if it was a $5 flashlight.
-After burning out two radios it is clear that your usage is beyond that expected by the designers, and therefore inappropriate.
Solution: Buy a flashlight, and promise not to use it as a radio!
-The manufacturer has bent over backwards to acommodate you, but don't be surprised when they refuse further repairs/exchanges.
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9
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eHam Forums / Antennas and Towers and more / RE: 20m "random" wire length?
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on: May 13, 2013, 07:53:04 PM
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As long as you your tuner can match the load, that is all that matters. When the tuner "matches the load", the antenna system is resonant by IEEE definition. The random length of wire winds up being one component in a resonant antenna system just as the caps and coils in the tuner are components in the resonant antenna system. Such can be proven by using a grid dip meter on the random length of antenna wire after the tuner is properly adjusted. Assuming the receiver has a 50 ohm input impedance, the GDO will indicate a resonant dip very close to the transmitter frequency after the tuner has achieved a match. http://www.w5dxp.com/OWT1.htmA wonderful discussion of antenna matching. I don't believe anything I have said disagrees! Cheers, bill |
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eHam Forums / Antennas and Towers and more / RE: 20m "random" wire length?
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on: May 13, 2013, 07:47:20 PM
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KB4QAA,
I think the point of the web page cited by K3ANG is that there are certain lengths that a "random" wire will be easier to match. Many of the tuners/couplers in use have difficulty matching a "random" wire that is very close to a half wavelength at the desired frequency. Some lengths manage to avoid that situation on all bands, and therefore the reason for such web pages. The antenna works "better", simply because it can be matched with commonly available tuners/couplers.
73 de wb0ksl
John
Sir, I absolutely agree with that that the thought behind the recommendation is to make matching easier. But the myth that is propagated is that 'random' antennas can/should be cut for specific lengths for better performance. This is untrue. If we choose to cut an antenna for a particular length (for easier matching, i.e. lower impedance) then it is no longer a random wire antenna. Further, the while matching may be easier, the antenna performance does not change. |
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eHam Forums / Antennas and Towers and more / RE: 20m "random" wire length?
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on: May 13, 2013, 12:50:07 AM
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Pure urban myths!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Any piece of wire will radiate. There are no magical lengths. The purpose of a 'random wire' antenna is putting up whatever is convenient or possible, not putting a tuned antenna. As long as you your tuner can match the load, that is all that matters. |
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eHam Forums / Antennas and Towers and more / RE: Hy-Power Dipole way out of band
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on: May 04, 2013, 08:30:28 PM
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Forget their numbers. That is for the antenna hung in ideal outside conditions.
You can only do one thing at a time. We must start with the "inside" portion of the antenna, 20 meters.
(resonant F - Desired F) / resonant F = Delta of Freq (in Percent) needed to change
Percent * antenna length = Amount to trim/add
So...
13.538 Mhz - 14.285 Mhz = 0.747 Mhz
0.747 / 13.538 = 0.0552 or 5.52% "too long"
17'10" (leg) *2 = 35.66ft (Present length)
35.66ft * 0.0552 = 1.97ft to shorten 20m antenna
1.97ft /2 = 0.98ft * 12" = 11.8" to shorten each side.
-I recommend not cutting the wire, just wrap around main wire until you sure of the length. You may have to adjust once or twice more.
-Keep the whole antenna intact, re-hang it and make measurements again.
40m will be done the same way. bill
This method will work for essentially any antenna assuming the adjustments are linear. It can save a ton of walking back and forth.
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