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   Home   Help Search  
Pages: Prev 1 ... 5 6 7 8 9 [10]
 91 
 on: Yesterday at 02:53:16 PM 
Started by KA4NMA - Last post by KA4NMA
Randy, Looking a Google Maps of your QRZ address, 144 Elm St, shows a Church at 143 and no 144.
The power lines to the Church and the home adjacent appear to be 240 VAC Triplex. The two hot lines are twisted around the neutral. The other lines appear to be cable and telephone. I would avoid all of these lines. BTW, the top power lines on the opposite side of Elm Street are High Voltage. It might be safer and more productive to place the antenna in the back of the home. I suggest you contact a local Radio club for a on-site visit. 73, Joe O, K I 5 F J, NNNN

I live in an apartment at the church. The address is correct.
Randy Ka4nma

 92 
 on: Yesterday at 02:52:22 PM 
Started by K9ZF - Last post by K9ZF
Thanks for all of the replies!

I'm sure I will make someone a very good deal.  But, I want to make a bit of money for the club as well. 

Good point about the crystals, I will take a look.

The best deals make everyone happy!

73 all, and if you happen to be at the Columbus Hamfest (IN) next Saturday, 4/1/17, stop and say hi!



 93 
 on: Yesterday at 02:50:01 PM 
Started by KE2KB - Last post by WB6BYU
Rather than using a 100V relay winding, I'd choose a standard value for whatever voltage you
happen to have available.  A 12V relay can be powered off some rectified and filtered AC from
the filament string.

Then arrange your PTT button to key the added relay.  One set of contacts switches the
receiver, and a second keys the PTT lead from the radio.  That automatically adds some
delay (the pull-in time of the HW-100 relay).

The problem, however, is that when you un-key the rig, the added relay drops out
first.  So you may have to add some "hang-time" to the mute circuitry.  There are
commercial "sequencers" that do this, and I'd probably try to do it using circuitry rather
than an added relay, as that allows you to separate the timing of keying the rig and
switching the receiver input.

 94 
 on: Yesterday at 02:46:16 PM 
Started by KA4NMA - Last post by KA4NMA
Randy, Looking a Google Maps of your QRZ address, 144 Elm St, shows a Church at 143 and no 144.
The power lines to the Church and the home adjacent appear to be 240 VAC Triplex. The two hot lines are twisted around the neutral. The other lines appear to be cable and telephone. I would avoid all of these lines. BTW, the top power lines on the opposite side of Elm Street are High Voltage. It might be safer and more productive to place the antenna in the back of the home. I suggest you contact a local Radio club for a on-site visit. 73, Joe O, K I 5 F J, NNNN

I live in an apartment at the church. The address is correct.
Randy Ka4nma

 95 
 on: Yesterday at 02:44:39 PM 
Started by KA4NMA - Last post by W8JX
I have a 69kv sub station about 300 feet from my antenna. I have never hard any noise from it that i could verify. The only effect I have noticed is it effects HF reception and xmit signal level in driveway next to it.  My driveway runs parallel it about 15 feet from pole line for about 200 feet before it turns toward garage and wires are about 50 feet up.

 96 
 on: Yesterday at 02:41:15 PM 
Started by KD7RDZI2 - Last post by WB6BYU
Quote from: KD7RDZI2

...I know air-core choke is worse then ferrite cores but I am a bit puzzled by the picture of the ARRL Book which shows the spirals which cross one over the other as they used just some tape. I did the same as the ARRL book but should I instead have perfectly wounded the coax...  or an easy wound ... has more or less the same effect...



Common mode currents and baluns have not been well understood by many ham authors, and there is a lot of
misinformation available.  It is unfortunate that W7EL's classic paper was tucked away in the
first ARRL Antenna Compendium rather than published in the front of QST where it belonged.
(But perhaps it stepped on a few too many influential toes...)  And it is rare that anyone actually measures
the performance of the chokes they recommend, but that is even more complicated, because it will depend on
the type of antenna, the cable lengths and how they are grounded, etc.


The primary issue with an air-core choke is the self-capacitance between the turns.  On one hand, you need
enough turns of coax for the choke to have a high enough impedance, but at the same time the more turns you
add, the higher the capacitance across the coil, and eventually as you get too many turns (or go higher in
frequency) the capacitive reactance exceeds the inductive reactance, and the coil acts like a capacitor
instead of a coil.  As you go above that self-resonant frequency, the choke becomes less effective.

Generally, trying to keep the coil in a neat spiral rather than "scramble-wound" will improve performance
because there are fewer opportunities for capacitive coupling from the first to the last turn, which could
be adjacent in a less tidy winding.  A bit of space between the turns will help to reduce the capacitance,
though also reducing the inductance.  Generally these differences aren't huge, but, given the relatively
narrow winding of good performance to start with, it could move up or down by a few MHz at the higher
end of the range.

So it's not a binary "this method works and that doesn't" sort of answer.  Some approaches may tend
to work better, but might not in a particular circumstance, especially when the choke is marginal in
the first place.  The real test is to build a current meter and measure the common mode current on
your feedline, then wind a choke and see how much it has changed.

 97 
 on: Yesterday at 02:36:57 PM 
Started by VE1FAL - Last post by G4AON
XPWare runs fine under Oracle Virtual Box, I have some notes on using it:
http://www.qsl.net/g4aon/amtor/

73 Dave

 98 
 on: Yesterday at 02:31:21 PM 
Started by KE2KB - Last post by KE2KB
Hi;
I need an antenns switch to isolate and ground my SDR while transmitting (100W max), both using the same antenna.
Rather than detect RF, I would like to use the transmit cw key-down or ptt signal to do the switching, while at the same time cause a slight delay before engaging the transmit relay in the rig. The rig is an HW-101, so I'm not sure what voltages are present at the CW key or PTT button, but I suspect it would have to be low enough to be safe to handle.
The transmit relay in the rig has a coil voltage of 120VAC, so the relay I use will need to be rated for it.
I would like to use a single DPDT relay - one set of contact to open the SDR's coax center conductor and ground it, while the other contacts close the circuit to enable the transmit relay in the rig to be energized.

Can I use any type of relay, or should I look for something in particular, so as to maintain a 50 ohm transmission line?
I am working HF (80-10m) with a diple or inverted Vee.

Thanks for your advice

Frank - KE2KB

 99 
 on: Yesterday at 02:20:16 PM 
Started by KE2KB - Last post by K4JJL
Put an ohmmeter on it and see if it's shorted.

 100 
 on: Yesterday at 02:19:02 PM 
Started by KE2KB - Last post by KE2KB
Hi;
I damaged an electrolytic cap while working on a power supply. A drill bit gouged a sort of channel into the side of the cap. It didn't go deep enough to cause the cap to leak, but it was deep enough to concern me about premature failure. This is a bran-new cap that I had replaced.
My first thought was to replace it. But I'm wondering whether that is necessary, if the cap isn't leaking or dented. I applied some JB Weld to the damaged area, just in case I decide to run the supply for a while before replacing the cap.
The supply is a Heathkit HP-23B for my HW-101. The cap is a 47uf @ 150V.

I am ordering a replacement cap anyway, but I may want to start testing the supply and the radio before I complete my order - I am still adding parts to the order, and don't want to pay shipping for two orders if I can help it.

Advice?

Thanks
Frank - KE2KB

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