Help needed ASAP with ant.

[FirefighterMC21]

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I have to send a voice transition from Cincinnati, OH to Indianapolis, IN. The supplies I have are a radio that will transmit HF at about 22 watts, a spool of military grade slash wire, a cobra head, and a mast that will raise up to 30 ft. I would prefer using a sloping V but could use a center fed dipole if needed. I need height length and take off angles and any other details that come to mind. The trans. freq also needs to be below 20mhz and the shot will take place at around 8am est. tomorrow. Please help.

 

[prcguy]

At that time of day 80m is a good choice and if both stations are running a horizontal dipole or inverted V (about 135ft center fed) at 20-30ft height you should work ok with 20w.

I routinely talk to a group every weekend about 10am between 1mi and a few hundred mi with a 20w manpack transceiver and a G5RV portable set up in a local park.
prcguy

 

[rfradioconsult]

Sound like another classroom exam to me, you want someone to give you the answer, good luck.

 

[FirefighterMC21]

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Not quite a class exam, listen in and you'll hear its not. We've tried using a field expedient antenna that was set up as a sloping v set in 15.5250mhz at around 4pm with no luck, just can't figure out the right take off angle.

 

[FirefighterMC21]

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And what is 80m? I don't know civilian terms

 

[prcguy]

80m is 3.5 to 4MHz range. That would give good results for what your trying to do with a low horizontal dipole from maybe 5-6PM local to 10-11am then switch to 7-7.3MHz for much of the day and maybe the 5MHz range late afternoon.

This assumes you are a licensed amateur operator with HF privileges.
prcguy

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And what is 80m? I don't know civilian terms

 

[FirefighterMC21]

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Well no I'm not ham, but I have HF privileges from a little higher power than the fcc. But thanks for the info

 

[captkel]

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Well no I'm not ham, but I have HF privileges from a little higher power than the fcc. But thanks for the info

I got to talk to god too

 

[zguy1243]

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I have to send a voice transition from Cincinnati, OH to Indianapolis, IN. The supplies I have are a radio that will transmit HF at about 22 watts, a spool of military grade slash wire, a cobra head, and a mast that will raise up to 30 ft. I would prefer using a sloping V but could use a center fed dipole if needed. I need height length and take off angles and any other details that come to mind. The trans. freq also needs to be below 20mhz and the shot will take place at around 8am est. tomorrow. Please help.

Can you share with us a little background on what you are doing and for who? Some more details will help. Will be happy to help once we know where you are approved to operate. This information helps pin down most technical details of your project...

 

[W2NJS]

Deleted. Not worth getting excited about.

 

[majoco]

I guess the ITU is a little higher than the FCC and they aren't going to be happy with you transmitting in a broadcast band on 15.525MHz, no matter what your Commanding Officer says.

 

[SCPD]

Hmmm.... maybe his "higher power" can give him the answer to his problem.

 

[FirefighterMC21]

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No, try us govt. Think about what a 21 is

 

[FirefighterMC21]

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We attempted every thing that every one suggested that was there today. We had a sloping v set up at 1/4 wave length, set up initially a at a 70 degree angle, pushing 22 watts at a little more than 8mhz with a 1.1:1 with no success. The mast was changed in height to change the take off angle multiple times in 3 foot increments all the way down to 40 degrees, and noticed that we were able to hear the other station keying up, but to heavy of white noise to make out any voice. All in all was better than previous attempt, but would still like to know why we can't get through.

 

[SCPD]

Wow... still seems like the "U.S. Government" would have the simple knowledge on how to properly erect field expedient antennas. Even the grunts I knew, when I was in Uncle Sams Army, could erect field antennas in their TOC for their PRC-77's and establish good comms. Lowly Ham operators can work the world using QRP, thats 5 watts or less for us "civilians" and/or non-government types, and a random wire antenna but the "U.S. Government" can't do it?

 

[FirefighterMC21]

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Ya know, ya don't have to talk down to people, I came here for help, not to be insulted. We only do an HF shot only once or twice a year. I figured some ham guys would be able to help since they mess with it a little more than we do. Every thing I've used CONUS and OCONUS has been uhf, vhf, or satcom.

 

[SCPD]

Not insulting.... you just alluded to working for/performing duties/handling a project for the U.S. Government in a cryptic sort of tone. It's my belief that anyone that is involved with any sort of communications duties/projects with the U.S. Government/U.S. Military would, or should, be trained in the aspects of the project/duties. Hell, even S.F. guys know how to "tune up" a tree and make a semi-efficient antenna out of it and your basic single channel R/T op soldier knows the basics of radio wave propagation(MUF, LUF, and MOF), efficeient antenna design, etc. Although I was a SIGINT analyst in the U.S. Army, the soldiers I encountered that had an MOS in something as simple as a single channel radiotelephone operator knew how to do what you're attempting. If you're looking for help some of the folks here were just asking for additional info to help you until you went into super secret squirrel mode by telling us it was for the U.S. Government and to "think about what a 21 is". There'e s lot's of info to be gleaned from this site if you're humble and not try to be a 007 of sorts.

 

[FirefighterMC21]

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I'm a field radio operator, USMC 0621. I'm attempting to maintain opsec, hence being vague in regards to every thing. And yeah I agree, I really like the theory behind HF and would have loved for them to teach us more about field expedient antennas than show us pics and tell us their names. I have no charts or cut sheets to say how far apart a sloping v should be or the take off angle, or what the off set should be for a counter poise for a center fed dipole depending on time of day, or distance. Oh and we weren't even attempting to use a covered net, it was single channel plain txt at 8.2520mhz. We initially tried 8.525 but had a lot of interference. Hopefully that helps.

 

[prcguy]

You mentioned the contact was at 8am and if that's the time you tested, 8MHz is not an optimum frequency. That might also be a bit high in freq for mid day NVIS between your two sites. Antennas should be horizontal since you want to transmit nearly straight up and down for the roughly 75mi distance you need. If you had more power a vertical antenna at each would probably work fine.

You should probably be using a propagation service like the one run by the Australian Govt. Check here:

IPS - Global HF - Hourly HAP Charts

Under "Global HF" select "HAP CHARTS", then your closest location would probably be Kansas City. From that location the colors will tell you the recommended frequency range for the distance you need to talk. You can transpose the color chart to your nearby location and the frequencies should be close enough. These maps are updated every hour and you can watch the critical frequencies change during the day/night.

So, have a few (horizontal) antennas on hand to cover the 2 to maybe 8MHz range and use the charts to select the best frequency for the time of day and locations you need to communicate with. Oh, and for what your doing don't give your exact frequencies away, especially on this forum.
prcguy

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We attempted every thing that every one suggested that was there today. We had a sloping v set up at 1/4 wave length, set up initially a at a 70 degree angle, pushing 22 watts at a little more than 8mhz with a 1.1:1 with no success. The mast was changed in height to change the take off angle multiple times in 3 foot increments all the way down to 40 degrees, and noticed that we were able to hear the other station keying up, but to heavy of white noise to make out any voice. All in all was better than previous attempt, but would still like to know why we can't get through.

 

[SCPD]

Mo betta Marine! I understand OPSEC but when you post it in a public forum people will want to ask a lot of questions. No harm no foul

Have you tried orienting the antenna differently? A sloping V is probably similar to a G5RV antenna that many Hams use and similar to a center fed dipole. As you know, a center fed dipole will have nulls and is bi-directional. Also, the two stations antenna polarity, horizontal vs. vertical, will have an effect too. Depending on your distance though sometimes antenna polarity between the two stations won't matter anyway. Time of day also has an impact as to what frequency you'll use too.

It may be too late with any assistance offered but we'll try to help. Have you ever considered getting your Amateur (Ham) radio license? You'll learn so much in the hobby that will help you with your MOS and in turn you'll look like a radio God to your fellow Marines. Ham radio operators do exactly what you're trying to do almost daily. Some aspects of the hobby include field expedient antennas on a mountain top using only a few watts. These guys have been known to "work the world" with a simple wire antenna, an antenna tuner, and a 5 watt transceiver using a battery pack. You'll hear these guys refer to it as "QRP". Our yearly Field Day excercise is suppose to test our ability to establish emergency comms using whatever we have on hand. When you get an opportunity search the net for info about getting your Ham license.