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Recent Posts

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1
Antennas / Re: EFHW observations and radiation pattern question
« Last post by vwflyer on August 14, 2019, 04:52:56 PM »
Hi Dylon,
You have a lot of good questions. I'll try to answer of few of them. I'm not an expert but I can pass on what i think I've learned. I give no guarantee of the accuracy of my answers.

It sounds like you have a good setup. I have found my MTR3b to be a great performing little radio and I have found QRP in general to be very effective. I've also used end fed antennas almost exclusively with QRP and they have worked well for me. That being said, QRP is a lot like fishing, if you don't stack the odds in your favor you may get a bite and you may not. Calling in the blind is the least optimum way of securing a QSO. Some days you snag a good one and some days you get nothing. When you are testing out a new antenna or radio it can be disheartening when your first trip out returns only minos. You have a great SOTA setup. If you self spot a SOTA or POTA activation you will stack the odds in your favor by bringing the fish to you. Now you are being chased by others who would have not know you were there or wouldn't have been interested in a contact with you otherwise. I have gone out on consecutive trips outdoors with my MTR and not had one bite. I started to wonder if my setup works. Then I go activate a summit (spotting myself) and in 20 minutes make 30 contacts nationwide using the same setup.

To address some of your questions specifically:
Half wave wire antennas when in free space (or when more than half a wavelength above the ground) radiate mostly broadside. They also radiate off the ends of the wire but not as much. As the wire is lowered below half wavelength to the ground the horizontal radiation pattern turn more and more omnidirectional. A 40 meter half wave antenna only 20 feet off the ground will have a mostly omnidirectional radiation pattern. As for the takeoff angle, it will be quite high and NVIS will work if NVIS conditions exist for 40 meters at the time and location of your activation. Ground losses will not be too high for NVIS if NVIS  is available. I have used NVIS very effectively with 3 watts. Your takeoff angle will be high, as I said earlier, but it will be low enough for a communication range of a few hundred miles in average conditions. I have found midday 40 meters to usually work well between 300 and 600 miles with my end fed antennas and QRP CW.
2
Antennas / Re: The Best Antenna Video EVER!
« Last post by Craig on August 14, 2019, 02:52:24 PM »
Sorry for replying to an old thread but I registered just so I could say thank you for the link to the most excellent video.

-Craig
3
General Discussion / Re: Hi from the Baltimoron
« Last post by gil on August 12, 2019, 04:02:01 PM »
Welcome aboard Alan!  :)
Gil.
4
General Discussion / Hi from the Baltimoron
« Last post by agilmore on August 12, 2019, 01:09:34 PM »
I thought I'd say hello to all the radio preppers.

Gil's YT channel is great, I've learned lots. Well done.

When I was a kid my friend and I both built 100mw voice transmitters for the AM band, hoping to talk between his house and mine. The 300 foot distance was just a bit too far. But it sparked an interest in both of us. He went on to be a DJ, then a station manager. I ended up being the corporate engineer for a handful of small stations.

Then I got into designing battery chargers. I worked for a couple of small companies...have you ever heard of DeWalt or Black and Decker?

Then I started designing electric cars. I converted three Smart cars (Mercedes) to fully electric.

Now I am retired and have lots of free time to sail and play radio. I've had my license for a few years and have lots to learn about antennas. My latest interest is in the end fed inverted V. Also, I'm learning morse code, but verrrrrrrrrrrrrrry slowly. Yes, I struggle like a lot of people...has anyone ever learned the morse code without struggling?

I am looking forward to reading the posts on this website about everything ham radio.

I agree with Gil about using solar or muscle power to power our prepper radios. All of my radio systems have solar abilities, both home and in the field. Have not figured out the muscle generator yet, but I think a model airplane brushless motor with an Erector set gear box might be a good starting point. Yes, I still have an Erector set for things like that.

73

Alan
5
General Discussion / Re: Cheap and easy communication setup for CB and HAM
« Last post by agilmore on August 12, 2019, 12:38:28 PM »
Yeah, that's pretty cool.

The radio is almost as small as the mic.

Hey, maybe they should put the mic element in the radio case, then there would be no mic, or cord, and it would be a lot smaller.

On second thought, forget that idea, real hams don't use walkie talkies :-)

Alan
6
General Discussion / Re: Hello from North Carolina
« Last post by Sgt. Silverman on August 06, 2019, 09:09:08 AM »
Thanks Gil!


73 - Greg
7
Antennas / EFHW observations and radiation pattern question
« Last post by dylan on August 05, 2019, 06:02:23 PM »
Hi everyone. I had a recent opportunity to take an MTR5b and 40m EFHW setup deep into the wilderness. Similar setup to last year's "radio vacation" (http://radiopreppers.com/index.php?topic=1482.msg13653#msg13653). The 40m EFHW was tuned via QRPGuys EFHW tuner, with driven element / counterpoise lengths from their recommendations. I was able to get the high end of the antenna up about 40 feet thanks to some conveniently placed trees and topography. Sounds like a great setup, right?

I found that I could "hear" stations all over the US at 0200 UTC (local time ~ 7pm) but could not make contact with a station about 50 miles away that was listening/transmitting. I used VOCAP (http://www.voacap.com/) to estimate the potential for said contact, and the predictions left me confident (see attached forecast). It seemed like 40m at 0200 UTC would be within the realm of possibility when using 1W CW on my end, and 15W on the other end. Note that the other station was using a 40m doublet at about 20 feet elevation, north-south orientation. I was north-east of the other station.

A couple of observations and questions for the group.

  • The EFHW + tuner combination seems to do well when the tuner is elevated at least 3-4 feet off the ground, any closer and it is difficult to achieve and SWR less than 2:1.
  • What kind of theoretical radiation pattern can one expect from an EFHF? I recognize that there are over 1,000 answers depending on the local conditions, but could there be any rules of thumb to go by? For example, one can expect maximum signal strength in the horizontal plane at 90 degree angles to the orientation of a 1/4 wave dipole at resonance.
  • Was the skip distance under those conditions / antenna the likely problem (overshoot) or antenna directionality?
  • Is it possible to achieve NVIZ-type communications with a EFHF?
  • Are gound-losses too high for NVIZ to function properly at < 5W of power?

Overall, I'd bring the QRP kit (MTR5b, 40m EFHF, QRPGuys tuner, mini-paddle, ear buds, 9V battery) on my next backpacking trip as it contributed very little weight.

I'll have it out again next week in case anyone would like to schedule a QSO on 20/40m.

73,
Dylan



8
General Discussion / Re: Hello from North Carolina
« Last post by gil on August 04, 2019, 03:34:32 PM »
Welcome aboard Sarge ;-)

Gil.
9
General Discussion / Re: Hello from North Carolina
« Last post by Sgt. Silverman on August 03, 2019, 10:24:40 PM »
BKMoore -

First, thank you very much for your service  :)  Second, I appreciate all the advice to learn CW, learn CW and of course... learn some more CW :D  I've been watching Gil and others videos on CW, and I can see where this is an important skill to learn.

73 - Greg
10
General Discussion / Re: Hello from North Carolina
« Last post by bkmoore on August 02, 2019, 08:50:46 PM »
Greg-

Welcome to the club. I was a Forward Air Controller in 2D Battalion / 3d Marines for several years. I think that's JTAC in Army lingo. I worked with the forward observers both in the field and in the FDC. Three words of advice: learn CW, learn CW, and lastly learn CW. In a field situation with small radios, batteries, field-expedient wire antennas, etc. CW is by far the most reliable means of communication.

73,

Brian
KM6ZYC
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