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 51 
 on: Yesterday at 09:06:53 PM 
Started by SCARPAD - Last post by N4UFO
Easy enough to add a third band...

http://www.eham.net/articles/7005

The 440 band is more or less the third harmonic of 2m... that's why the UHF 1/4 wave vertical section will work with the 2m ground plane. But 220 is not related, so I doubt it would tune up just sticking another vertical element on it.

73, N4UFO

 52 
 on: Yesterday at 09:06:05 PM 
Started by BRIANBURNS - Last post by VE3LYX
I have also a homebuilt rig based on the Electronics Illustrated article of 1968. This is known as the Bare Essentials Transmitter. It used a 50c5 tube however I used a 50L6 since I had one and they are electrically equivalents. I  changed that to a 50c6 a few years ago as it is same pinout and heater voltage but a stouter tube. This has been a fairly successful rig with several QSOs between 180 and 300 miles away. In light of my AM interests and our discussions here I tried series modulating it this weekend with a simple series cathode modulator using a triode in place of the key (it uses cathode keying) and driving that with a carbon mic , a battery and a old Audio transformer.  In testing it works very well. The parts count is low and construction easy. I am now testing on 3736kc  when I can. Please if you have time and are within range listen for me . The carrier has a distinct hum because of the PS design so it is easy to locate even in QRM. It goes away when I modulate. If you want to sked a contact after dark just ask. If it turns out as good as it appears to be in testing I will build another just for this purpose. It is crystal control so 3736 is the only phone band rock I have.
don

 53 
 on: Yesterday at 09:01:40 PM 
Started by N3DT - Last post by WB6BYU
Ok, using 1 1/8" down to 7/8" diameters with 66" spacing:

If you want to use the DK7ZB feed method (28 ohms) then make the director 128" each side of
the boom and the driven element 137".  That models at 6.6dBi and 11dB F/B.

With a 150pf shunt capacitor beta match (meaning you just connect a fixed capacitor across the
feedpoint - you'll have to make sure it handles your full output power) I'd start with 139" on the
driven element and 134" on the director.  That gives about 6.8dBi.


By comparison, using a shunt coil beta match on a reflector you could use lengths of 140" on the
reflector and 126.5" on the driven element.  This gives about 6.6dBi gain, and the shunt coil is
about 0.31uH.

Or if you don't want to bother with any matching, use a driven element of 137" and a director of
125".  That gives you a 50 ohm SWR better than 1.5 : 1 across the whole 15m band, but only
5.7dBi of forward gain.  Of course, in that case you could use a Moxon, which could give an even
better SWR with a bit more gain and excellent F/B ratio.

As a point of reference, all the beta match versions were designed for 25 ohms.  You can get a bit
more gain by adjusting for a lower feedpoint impedance (using 180pf rather than 150pf) but the
bandwidth starts to suffer, and constructional tolerances become more critical.



Any of these variations should work.  In practice, you might not notice much difference among
them.  There is about 1dB maximum difference between the wide band direct feed version and the
optimized version with the shunt capacitor.  The F/B ratio is around 10dB for all of these.  (F/B is
always poor with a standard 2-element yagi unless you are willing to give up some forward gain
and use a very short boom.)

 54 
 on: Yesterday at 08:54:01 PM 
Started by WI9NDY - Last post by K1ZJH
Hope you have the money and resources to get an AM license!  Even the expanded AM band is full. Of course, the same few hundred K will you a shot a grave yard station that is going, or is already, bankrupt. And forget, you have to pay for the programming rights.

 55 
 on: Yesterday at 08:50:27 PM 
Started by N2CJ - Last post by N2CJ
Has anyone every used a surplus telco splice to provide lightning protection for rotator cable? I was looking at a surplus unit (Western Electric 116C) With twelve terminal posts, it seems ideal for this application. The lightning protectors that are sold for this purpose are not cheap.

 56 
 on: Yesterday at 08:47:55 PM 
Started by M6GOM - Last post by W6RMK
Sort of publicly. You have to execute a fairly lengthy license agreement before you can see it. The agreement isn't all that unusual in its terms.. somewhat less restrictive than, say, the Apple iOS developer license, but a long ways from the original Flex "everything open under GPL".

Specifically, no reverse engineering; no use with other kinds of radios; no competing with Flex; etc.


 57 
 on: Yesterday at 08:31:07 PM 
Started by KG9SF - Last post by W8JX
Forgive me, guys.  I'm a low-vision OT who's looking for a new 2M/440 mobile rig.  I've looked at Kenwood, Icom, and Yaesu, but it's awfully hard for me to gather all the details without spending hours looking at a single webpage.

Anyway, icom seems to make only one non-ldigital radio, and that one is 2M only.  Ken wood and Yaesu don't seem to be making ANY non-digital 2M/440 radios.

I don't want to jump into digital until some format agreement is reached.  The social security check only goes so far.

Anyone have thoughts or ideas about this?

Thanks and 73,
Scott. KG9SF


They are not digital mode radios. They are microprocessor controlled but they all are now. Icom makes a few rigs that are digital though. 

 58 
 on: Yesterday at 08:29:20 PM 
Started by VY1MR - Last post by N3DT
I would find that surprising, but stranger things have happened. How big is the tractor? Lawnmower or JD2040 or even bigger?

 59 
 on: Yesterday at 08:29:00 PM 
Started by NC5T - Last post by K4RVN
The tune position on the Omni is used to tune the amp and then it is switched to the SSB operating mode or CW . I had mean to ask the op if he were in the SSB mode talking into the dummy load on his posted readings or was it the tune mode  but I forgot. The SSB would be probably 20 to 30%  of the tune readings, or  CW in actual operation. I too would not know how to tune in the SSB mode if it can be done. Also, My voltage is a nominal 240 supply, not 230. Bob have you measured yours. Mine in the summer sometimes measures 240 plus a few. My HV runs 3150 unloaded.
My amp is set on the 230 volt transformer tap . I used to have 230 here back in 1989 when I bought the AL80 A, and I just set the AL 80B on the 230 tap about 6 months ago when I bought it as the third owner. It doesn't hurt it from my experience .

 60 
 on: Yesterday at 08:28:20 PM 
Started by W6GX - Last post by W6GX
It is a real challenge working DX from a small lot.

I'm under the impression that except for a few stations ALL of us have a small lot Smiley  When it comes to the low bands 'size' is all relative Cheesy

Congrats on your new RX antenna.

ps Congrats to Rich on the new one on 160m.

73,
Jonathan W6GX

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