Re: Topband: Detuning Relay Flyback Diode

If you have any diodes in a switch box or the like, be sure to add a bypass cap across the diode - 0.01 uF will do.  Diodes are great harmonic generators (and mixers) and equipment connected to control cables or feed lines often is pretty hot with RF current. That includes rotator controllers,

Re: Topband: Common mode choke 160m inverted L

Hi Gurt, With only two radials on your inverted-L, you should use a good common mode choke on your coax. The W2DU style choke on only one meter of RG-393 will not be very effective Suggest you read this excellent reference: http://k9yc.com/CoaxChokesPPT.pdf 73 Frank W3LPL

Re: Topband: Common mode choke 160m inverted L

Hi Gert, What you are suggesting, *** at 1.8 MHz ***, even with 34 of those cores on a 1 meter length coax would have only a few hundred ohms blocking, not nearly enough blocking to do anything serious. It might somewhat knock down back-feed of noise from the house running out to the antenna, but

Re: Topband: Detuning Relay Flyback Diode

The back emf diode slows the relay a lot and you can improve that with a resistor in series, fudge as required. Here's another method: in the drive transistor circuit, fit a small capacitor between collector and base. As the back emf builds up, a current will be fed back to the base which will

Topband: Common mode choke 160m inverted L

Hi All, I would like to build a good high power common mode choke for 160m. I have a piece of RG393/U ptfe 10mm coax. (1 meter) I was thinking of using this and make me a "W2DU style" choke. Searching for the ferrite cable cores, i found on the Mouser website 2 types which would fit: Fair-rite

Topband: Detuning Relay Flyback Diode

Date: Sat, 23 Dec 2017 10:51:57 -0500 From: Brad Denison To: topband@contesting.com Subject: Topband: Detuning Relay Flyback Diode http://w1nt.com> ## I call em back emf diodes.Use a single 1N5408 or 6A10 diode, reverse connected across the 12 vdc winding. Heres the simple fix to SPEED

Re: Topband: Detuning Relay Flyback Diode

Tim, Yes the end intent is to have the K3 key both an amp and the detuning circuit. Would you happen to have an example of the series diode circuit you are referring to? Seems better to implement this vs. creating relay delay. Thanks, Brad W1NT On Sat, Dec 23, 2017 at 11:05

Topband: 160m/80m antenna

hello i am after a good 160/80m band antenna is there any good info ?the main problem as i see is hard to find this [BLACK cable as in use on company call MY ANTENNA ] where can i buy this cable ? i have other  they are to heavy for the job happy  holiday to all vy 73 elan g0uut

Re: Topband: Detuning Relay Flyback Diode

You can put the diode directly across just the LED if the relay speed is important.  The LED series resistor won't slow it much. On 12/23/2017 11:15 AM, Paul Christensen wrote: Brad, If you use an LED with a dropping resistor across the coil to monitor relay status, then you must use a fly-bac

Re: Topband: Detuning Relay Flyback Diode

Brad, If you use an LED with a dropping resistor across the coil to monitor relay status, then you must use a fly-back diode. The coil of the type you're using will produce substantial EMF as power is removed and the coil field rapidly collapses. The collapsing field will produce E-I beyond the

Re: Topband: Detuning Relay Flyback Diode

Whether a flyback diode is needed depends on what is driving the relay and whether it needs snubbing. Adding a flyback diode substantially lengthens the time it takes a relay to open, which may or may not be an issue. What was a 6ms relay will become several times longer on open. There are better

Topband: Detuning Relay Flyback Diode

I have a couple of 6ms 12V Kilovac relays wired up as a detuning circuit during RX. One question comes up before implementation regarding flyback diodes - would they be needed? Seeking opinions on this question. The relays are powered during TX and not powered for RX direct keyed by the radio wi