Search results

I hear you with the data sheets....lol I couldn't find the 7530 data sheet to compare it too. They are both 70 watt To-220 transistors. I would be willing to bet there isnt much difference. The IRF transistors are not tested for use in a RF environment. I think the ERF transistors were...

I know the IRF520 work great in-place of the ERF2030's Look into the IRF530 to replace the ERF7530's, they can be had for around a $1 each. (havens personally tried them)

Its not perfect, there is some mismatch. Captain nailed it.

Its normal to have a quieter receive with it on. That was my point, you dont need two radios for it to work.

"inductive reactance" :whistle: ohh ok Thanks for clearing that up guys! :LOL:

Mix 31 with 7 turns of RG8X with a 4 diameter. makes a great balun/choke and creates inductive RESISTANCE at the giving target frequency. That effective frequency is below 10mhz and not as effective at 27mhz.

I think they stuck with that length because the truck stop 18' foot half wave isn't even close to the real electrical half wave. Depending on the velocity factor of the coax the real half would be a great recipe for burnt lips.

1/4 wave is capacitive a longer than a 1/4 wave is inductive. 3/4 wave will also work, its not ideal but it works better than most crappy baluns people buy or build. Edit: You are correct there is no optimum length for a properly terminated transmission line. However when there is common mode...

At that frequency and length the common mode is not present, It works a lot better than most chokes. Most of your so called chokes are a band-aids, a lot of operators add chokes and all they are really doing is adding more inductance or capacitance. Not adding the needed resistance to "choke"...

I remember doing it as a teenager, picked it up from an older radio operator at the time. Here is a site that I found that talked a little more about it https://www.w8ji.com/common_mode_current.htm

It doesn't reduce common mode current a 1/4 wave feeder the common mode current is at a minimum, 1/2 wave feeder the common mode current is at a maximum.

Well not necessarily, I tune the coax for a perfect 1/4 wave length to reduce common mode current instead of using a balun. Its a perfectly acceptable way. Mobile antenna installation are most often slightly imbalanced.

But thats no from Cobra, its just another radio myth that got started and now everyone believes you need two radios for Sound Tracker to work correctly. The Sound Tracker only operates as a expander/compressor for RX/TX, in mobile applications it actually helps a lot. Straight from a Cobra...

Can you post the info from Cobra that it requires two radios? As far as I understand it work as intended just by itself. Cannot tell a difference between people who are running ST or not.

Could you cut strips of copper clad board, stand it up on end notch out some for clearance and solder it to the ground on the foil side in multiple locations? ____________________ |__-----___----____----___|

Thats really interesting! How was the ground modeled between the two antennas?

Thanks Marconi however the link didn't work. I saw that discussion a while back, I haven't taken the time to read it maybe its time I should!

I was always told 72 ohms never measured..... Or am I confusing that with a standard dipole?

I personally like the Sound Tracker. If you want to monitor a channel the ST acts like a automatic gain control knocking a lot of static/white noise out. If you get an amp with variable power, you can turn the power on the amp down and run the 4 watt dead key into it. I have a KL 503 the amp...

Short answer is NO, coax doesn't change the SWR only the antenna can. If your antenna is a 50 Ohm load no special coax lengths needed. If your antenna is anything other than 50 ohms (ie swr greater than 1.5:1) Or you have some common mode issues, then coax length make a huge difference. You...