[MRCA] M&S Net antennas

[Al Klase]

Hello Ray,

It was good to hear you on the net the other day.

The fundamental mode of operation on M&S is NVIS.  So, you want a strong 
vertical component to your radiated signal.  That means a horizontal 
antenna.  An 85-foot dipole is probably the easiest place to start.  
Even an inverted-V with the center up 15 feet and the ends almost on the 
ground will get the job done.

As you discovered, a vertical can be heard, but is at a real 
disadvantage especially for the first 100-150 miles.  As Alex pointed 
out, the -6 dB from 100 watts to 25 watts is likely to put you down in 
the grass.

One of my favorite drawings:



This was a horizontal dipole versus a 10-ft whip, but even if it's a 
1/4-wave and radials getting you another 20dB, it still sucks for NVIS.

Personally, I use a 100-ft doublet fed with 300-ohm twin lead.  This 
requires a tuner, but it will go almost anywhere.  I don't have room for 
extensive antennas here in Jersey City.

Al




On 1/29/2013 10:22 AM, Ray Fantini wrote:
>
> Wanted to get something up and working for the M&S Net, got lots of 
> radios so that's not an issue but the problem appears to be antennas. 
> Over the last couple weeks I have discovered a couple things. First, 
> of all the low frequency antennas I have installed at the QTH the only 
> good antenna I have right now is a half wave inverted V cut for 160. 
> My other two dipoles cut for 40 and 20 meters both have coax full of 
> water. Who would have thought that if you have the ends open where 
> they connect to the center sections that water would get in and 
> eventually come out the end of the cable in the shack, I was 
> surprised! Second, nothing I have appears to resonate at 5.3 Mc and 
> antenna tuners are harder to just throw together than first thought. 
> Third, I know nothing about antennas and propagation.  can tell you 
> all about VHF and microwave path analysis but this HF stuff is all 
> voodoo, when everyone starts all the arguments about NVIS and the like 
> my eyes just glaze over.  So with all this in mind this last weekend I 
> strung up a vertical wire insulated  one foot out from the top of the 
> tower down to an insulated support about thirty feet to a box with a 
> taped coil and capacitor in it tuned for minimum reflected power back 
> at the radio. I think this would be a vertical antenna, although do 
> not know if it's affected by being that close to the face of the 
> tower. The problem is general consensus was that just about everyone 
> who was able to copy me says my signal sucks, so now it's time for 
> some improvements on my end. First question: is a vertical antenna 
> worth using? Can the poor performance be an issue on not having enough 
> radials? Would there be an advantage to shunt feeding the antenna to 
> the top of the tower? Or am I just wasting time working with a 
> vertical in the first place? And that leads to the second question: 
> would it be better to just throw together a dipole cut for that 
> frequency and put that up? Or maybe the same antenna as a sloper or 
> inverted V?
>
> RF
>
>
>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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