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 on: Today at 09:10:15 AM 
Started by AG5T - Last post by NZ4ZN
" short."

?? Huh of the very worst things that could go wrong.

 on: Today at 09:09:40 AM 
Started by W6EM - Last post by W6EM
Quote from: W6EM
The BF908WR has typically over 40 and up to 50 mS of forward transconductance.  The BF998 is only about 24mS.  Although its not much, when you look at a 40673 for reference, a double, triple and quadruple of voltage gain might be worth it.  If I can find another device that comes close to mid 40's to 50 mS, then I'll abandon the BF998WR.  So far, nothing comes close that I could find.
Won't excessively high gain be a problem? Beyond a certain point it won't boost noise figure, which is largely set by the circuit. Very high tranconductance is useful in a wideband circuit, but we usually want narrowband preamps etc.
Not sure, but I don't think so.  Recall the old WE 416B triode?  The transconductance for them was about 50mS as I remember and were used widely in microwave receivers as RF amps.  Grounded grid, though.

The noise figure for the BF908WR is higher.  It's 1.5dB whereas the BF988 is about 1dB at 200MHz.  Don't think either would be a problem at HF, but don't know.  The extra voltage gain would be worth it if not unstable.

 on: Today at 09:05:36 AM 
Started by VK3BL - Last post by KM1H
And Id surely advise against putting in a higher voltage transformer and add two more filter caps, etc as the tank circuit is already pretty scrawny to handle 3-4 572B's at 2400V or so.


 on: Today at 08:46:55 AM 
Started by KT0DD - Last post by N8FVJ
Pulling at strings trying to figure out why the TS-590SG is so much better vs the ICOM IC-7300. High-end tube audio cleans up after 25 hours and refines in 100-200 hours. I heard it.

 on: Today at 08:46:52 AM 
Started by KF7DS - Last post by KM6AXC
After quite a few years of concentrating on the high bands, it is now time to get 80m capable. I do not have enough site area for an 80m dipole, nor enough available tree height.

My 40m and 30m dipoles are up 45' and 35' feet at their peaks, respectively and work well - more omni-directional since they are lower than optimal.

I do have enough room with work with an endfed, and was thinking of a MyAntenna's 8010, as well as an Alpha Delta DD (80m and 40m) center fed dipole. Run between shack and feedpoint is about 135'...I could get either up with the centers at 45'; however, the ends will only be around 20'-25' high and the endfed may work better in that situation...thoughts?

Yes!! the end fed will work!!  I have 5 of those puppies in my back yard covering all bands except 17.  No counterpoise or radials have ever been necessary nor have I ever encountered RF in the shack.  Of course, I use only 100 watts.  Can't say what would happend with the big power guys.



 on: Today at 08:41:50 AM 
Started by KT0DD - Last post by K0OD
"Perhaps all the software requires break-in time? I heard of that in high-end audio electronics"

First time I've heard that. Any truth? Sounds like something a salesman would say if you tried to bring back your high end sound system.

 on: Today at 08:37:27 AM 
Started by KC7RYS - Last post by KM6AXC
Is a tuner required?  Well, the answer from the manufacturer is no, one does not need a tuner.  And, that is probably true!!  I just use a tuner with everything - thinking that is the way to do it:)Smiley  I just buy buy buy, put all the stuff together as if I knew what I was doing, and hope it works:)Smiley.  So far, all does indeed work.

Here is what I did/have done.  I have 5 of those end fed things things.  So easy and convenient!!

I know enough about antennas that "height is good".  Also, I know that installing a sloper configuration is both easy and it works!!.  So, for each end fed antenna that I have/use, I bought one of those MFJ telescoping masts (not the flimsy ones, the ones more sturdy with thicker walls).  At antenna installation, I then hoisted up the mast section by section (do not rely on the sections to maintain there grip just from hand tightening - the wind motion will work the sections lose and then you get one hell of a big collapse of section after section collapsing on the other - use instead hose clamps at each section "join point").  At the completion of each section hoisted, I tied off the other end to a convenient tree limb form my "sloper".  I then trudged back into the shack (my den actually -  but I need to use proper jargon to maintain good "ham" status) and wrote down SWR/frequency/"how close to resonance" that section created.  I did that using the Rig Expert antenna analyzer.  Such a tool is well worth the expense.  I then trudged back down into the lower 40 where the sloper is, unhooked the end that was tied to a tree, went back to the telescoping mast and raised it yet ANOTHER section (and clamped it off).  Went back to the tree to secure the sloper end, trudged back to the shack to do the measurement associated with that next section.  Then I repeated the whole process until measurements were available for each section of the telescoping mast. 

The bottom line is I found that a nice low SWR of 1.3 indeed materialized like the manufacturer stated without the aid of a tuner.  That SWR appeared just after the fifth section of the telescoping mast was up and secured - along with the other end tied to my tree of course.  Therefore, it appears that one can do the deed without an antenna tuner.  But, because I buy buy buy and use everything I can get my hands on, I nevertheless have the thing running through my tuner anyway.

The good thing about these forums is that more folks will chime in with their ideas which either work just as well or even better.  I always welcome other/new ideas (but mine of course are the best - heh heh heh)


Jerry (I forgot the "Y" on my first response to you)   

 on: Today at 08:26:59 AM 
Started by ONAIR - Last post by KC8KTN
Good grief, where did all of that come from?  Been hanging around K9MHZ  lately?  Flame on, have fun.
Wow. Listening to a bitter/jealous  K9MHZ. WOW. 73s to all.

 on: Today at 08:20:54 AM 
Started by AE5X - Last post by W1VT
This site allows you to independently run both SP and LP predictions between two points.

Zack W1VT

 on: Today at 08:20:13 AM 
Started by KJ6FPJ - Last post by K4JJL
Probably desensing your receiver.  You're going to need a cavity tuned to your RX freq so the TX doesn't overload the front end.

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