-
Posts
-
Back in the day most RF related electronics used a 50 ohm coax with PL-259 or SO-259 Connectors.
Now, I’ve seen a change to N-type connectors and BNC connectors, which is fine.
But, why has the 75 Ohm F type connector been introduced into the FM transmitter category?
I have seen the F connector used on Ramsey Electronics products such as their FM transmitters kits and also on their Low Pass FM filter kit. I bought this kit and assembled it per the instructions. It came with two female F connectors that would only fit 75 Ohm coaxial cable, not RG8 coaxial cable or other 50 Ohm coax.
I have to wonder if this filter was designed to work with 75 Ohm coax only and using a 50 Ohm coax would be a mis-match.
Bruce.
Total posts : 45366I think the simple answer is F connectors are cheap. F connectors are used by cable TV, satellite TV, and OTA TV. That is a pretty big base for economy of scale to bring the prices down. Also, the 75 ohm 50 ohm mismatch only costs 0.2 dB. (http://www.ham-radio.com/k6sti/match.htm)
Add on top of that that a compression F connector is easy to put on a piece of coax and custom cables become easy to make. The 1 page instructions that come with a compression connector kit are adequate to let people get the compression termination of RG59/RG6 good enough that it will last for a few years if not more.
On the other hand there are entire pages of HAM sites and forums dedicated to getting a PL-259 installed correctly.
Total posts : 45366And ………………….. a dipole, with no reflectors and directors has an impedance of 75 Ohm!
Rob V.
Total posts : 45366You could connect your FM Transmitter to a Radio Shack outside Beam and beam your signal in the direction you want to go. If the higher uV/M becomes legal well you could get 3 miles on a beam and little power out of the FM Transmitter. I’ve seen this done years ago and the results were not too bad.
Total posts : 4536675 ohm cable is cheaper as well. I use a 100 foot run of RG6 (75 ohm) in my amateur radio station and it performs better (connected to my vertical) than the cheap RG-58 50 ohm cable I used before.
Total posts : 45366What bands do you like to work?
Total posts : 45366I like 80 and 40, occasionally 20. 10 can be a lot of fun when it’s open.
Right now my antenna system is pretty compromised. I have a set of Hustler resonators that I switch between on my car, and run that RG-6 from my ham shack inside through the garage and to the car. It still does a pretty good job, all things considered.
Total posts : 45366TNX. I have a friend who lives in a deed restricted community in S. Florida. He uses a Tar Heel with the cabling for the remore control and coax running underground to the inside of his house. Actually works quite well.
80 and 40 is out for trying to get to your neck of the woods during the summer. Lightning static is off the charts down here. 20 is the best bet or maybe 17.
73, me
Total posts : 45366
Total posts : 45366John, maybe we can set up a QSO sometime after next Tuesday (I have family visiting for about a week starting tomorrow, and it takes a bit to set up the antenna on the car, run the coax, etc.). I’ve never had much luck with 17 meters, so 20 is probably the way to go.
Total posts : 45366OK. NP. Just let me know. I am guessing you are 3 time zones away?
Total posts : 45366In all my days of using the citizens radio band, I used double shielded RG8 coax. The exception being mobile installations.
I had that radio shack crossbow 3 element beam and their .64 wave ground plain antenna. I used the 3 element for horizontal communications and that ground plain for vertical.
I had the Realistic Navaho TRC-490 40 channel SSB transceiver as my base station.
I dropped out of CB in 2008 and sold most of my equipment. I still have a full collection of Secret CB/Radio Secrets books volume 1 through 30 and a large collection of other books related to CB mods, as well as SAMS photofacts and service manuals and a few O2A, UPD858 and MB8719, cybernet chassis for parts. Interesting I still remember those chip numbers as I have not worked on CBs since 1994.
The last radio I got rid of was the Uniden HR-2510. Someone recently gave me a Ranger RCI-2950. It was originally given to them as a gift by me back in 1994 and they felt it should go to me as they no longer have intentions of ever using it. It was in use for about a year and put into storage since 1995, so it is still in mint condition.
In my history, I have used BNC connectors, but mostly for scanner antenna applications. The PL-259 male connector was always my preference in two way communications, unless I was otherwise restricted to the thinner 50 Ohm coax, it’s been so long since I used it I forgot what type it was called now, perhaps RG58U?
I can understand the use of BNC or N-type connectors on transmission lines, but still can not understand the use of F-connectors commonly used on cable TV or audio/visual equipment such as VCRs. I excluded DVD devices because it is my hope that most of you use the HDMI port on these devices.
I have to wonder how the use of F-connectors in citizen band cable connections and applications would affect the impedance.
I am not really looking to go back to CB anytime soon, so my experimentation there is not a near future possibility.
Bruce.
Total posts : 45366Yep. I’ve had the best luck with 20 early evening my time.
Total posts : 45366I remember the RG8 was the thicker coax for CB and RG58u was thinner and used for mobile. I did find a mobile scanner antenna that also used RG58u coax. I did have a police scanner antenna that had RG8 coax with a BNC connector for the scanner. I don’t know why these scaners went to BNC maybe because it was smaller. I didn’t like the type of connection the BNC made however not as snug as PL-259 or even a TNC connector. I’m actually surprised the scanners didn’t use the TNC if they were going to use a smaller connector. When you screw it in it is really nice and snug and no play in it meaning a more solid connection. I know FM does nice with RG58u but not so sure with RG8. I can see FM Transmitters using the F-connectors because 75 OHM may work nice for microbroadcasting.
- You must be logged in to reply to this topic.
