Using F-Connectors with 50 Ohm RG8

[WA8ZTZ]

You don't mention how much power you are running or what the path is like to the repeater 22 miles away so the fact that you can hit it may not mean too much.
Otherwise, there is a 1.5:1 mismatch at every 50/75 transition. So, your 1.3:1 SWR may be higher due to some return loss in the cable run.
IMHO, you would be better served to run either RG6 or RG58 alone all the way without all the transitions.
With RG58, you have a 50 ohm match. However, RG6 has lower loss. The 1.5:1 75 ohm to 50 ohm mismatch with RG6 is not a big deal in the overall scheme.
It's your choice, go with whatever you feel works best for you.

 

[GregOH]

You don't mention how much power you are running or what the path is like to the repeater 22 miles away so the fact that you can hit it may not mean too much.
Otherwise, there is a 1.5:1 mismatch at every 50/75 transition. So, your 1.3:1 SWR may be higher due to some return loss in the cable run.
IMHO, you would be better served to run either RG6 or RG58 alone all the way without all the transitions.
With RG58, you have a 50 ohm match. However, RG6 has lower loss. The 1.5:1 75 ohm to 50 ohm mismatch with RG6 is not a big deal in the overall scheme.
It's your choice, go with whatever you feel works best for you.

I'm using a 5w HT and the terrain in the path to the repeater is not flat. I also TX to and RX from a UHF repeater that is in the same area as the other I mentioned, but the swr must be much higher which is why I plan to switch to a dual band roll up Slim Jim. Once I get the roll up Slim Jim positioned outdoors, I'm hoping that it will perform better than the quarter wave ground plane antenna I'm using now.

So the plan is to remove the RG6 and use RG58 all the way and see what that gives me. If it works well, I may try to find a UHF/VHF amp to increase my power.

 

[prcguy]

I would remove the F connectors in the wall plate and replace with a double female BNC or use a BNC chassis connector with RG-58 or RG-8X inside the wall. I don't think your going to find an easy to install F connector for RG-58 to the radio but BNC is cheap, easy and everywhere.

 

[mmckenna]

Once I get the roll up Slim Jim positioned outdoors, I'm hoping that it will perform better than the quarter wave ground plane antenna I'm using now.

Don't expect a big difference.

A quarter wave with ground plane is considered to be 0dB gain.
A J-pole is a half wave antenna without a ground plane. That'll have 0dB gain.

Unless you are adding a ground plane under the J-Pole, there will be little to no difference in performance.

 

[GregOH]

I would remove the F connectors in the wall plate and replace with a double female BNC or use a BNC chassis connector with RG-58 or RG-8X inside the wall. I don't think your going to find an easy to install F connector for RG-58 to the radio but BNC is cheap, easy and everywhere.

The Slim Jim has 16' of RG58 hard wired to it and has a PL259 connector on it, so I planned on removing the RG6 connector from the wall plate and running RG58 from the radio through the wall to the PL259 connector.

 

[GregOH]

Don't expect a big difference.

A quarter wave with ground plane is considered to be 0dB gain.
A J-pole is a half wave antenna without a ground plane. That'll have 0dB gain.

Unless you are adding a ground plane under the J-Pole, there will be little to no difference in performance.

What would be the best way to add a ground plane to the j-pole? I was thinking with it being half wave, a ground plane wouldn't be required.

 

[mmckenna]

What would be the best way to add a ground plane to the j-pole? I was thinking with it being half wave, a ground plane wouldn't be required.

A ground plane is -not- required for a J-pole/half wave antenna. However, in this configuration it provides 0dB of gain, same as a 1/4 wave.

Adding a ground plane under the half wave/j-Pole will change the radiation pattern and focus a bit more towards the horizon. Usually this gives about 2.4dB of gain. Not a huge change in performance, but better than zero.
Some 1/4 wavelength long radials under the base of the antenna connected to coax shield would work. How you do that with your specific antenna will depend on the design. Since you said the coax is permanently attached, accessing the shield at the base of the antenna will require stripping the jacket off the coax.

 

[prcguy]

What would be the best way to add a ground plane to the j-pole? I was thinking with it being half wave, a ground plane wouldn't be required.

There are no specific plans I've seen for adding ground radials to a J-pole. That would probably detune it and require some fiddling, not to mention the mechanical hurdles.

 

[G7RUX]

There is no real issue with using 75 ohm coax for your system. There will be a small mismatch loss but it may well be outweighed by the reduction in overall attenuation depending on the types used.

 

[GregOH]

There are no specific plans I've seen for adding ground radials to a J-pole. That would probably detune it and require some fiddling, not to mention the mechanical hurdles.

I agree with nothing out there to add ground plane radials and I won't be doing so. The NT9TAXLABS dual band Slim Jim antenna will be positioned in it's "sweet spot" outdoors just like the quarter wave ground plane antenna I'm using now is, and if I don't like the results, I'll continue to do things to get the improvement I'm looking for (which don't have to be much better than what I have now).

In my mind, experimenting is what makes this hobby fun and with what I'm doing at the moment, it's not breaking the bank.

 

[ArloG]

Well. For some reason I'm still getting alerts on this topic. And it's all good.
Great stuff here. But. If you can, why use coax of a different impedance than the radio and antenna they were designed to use at all?
Too easy to just do it right. Good cable is easy to get. Ebay roll ends. Buy by the foot. Not chinesium knock-off junk. Too easy.
Buy once, cry once. Do it right the first time.

As far as a ground plane and how to do it with a slim jim, j-pole. Whatever. Not really knowing how long the factory pigtail is.
A male-female bulkhead connector. A sheet of hobby store brass or copper cut to your desired dimensions Some hardware. Solder your Radials-d-jour to the copper flange..
Spray it with Flex Seal to weatherproof it all when satisfied.
And Bob's your uncle (but mom knows different)
Get crafty.

 

[cavmedic]

Do the next tenant a favor and not mix 50 ohm cable with 75 ohm connectors. All that will do is screw them if they decide to use that outlet for TV or Internet and can’t because they think it’s a standard coax outlet.

 

[prcguy]

Do the next tenant a favor and not mix 50 ohm cable with 75 ohm connectors. All that will do is screw them if they decide to use that outlet for TV or Internet and can’t because they think it’s a standard coax outlet.

The next tenants will most likely not be hams. Screw um!

 

[cavmedic]

The next tenants will most likely not be hams. Screw um!

Well, I’m thinking more along the lines of the installer who is trying to put food on his table and gets screwed on his metrics and or money because some idiot at corporate said an install should only take xyz time / pay $xyz, and has to fix the previous install done by Jonny Homedepot, Larry Lowe’s and Captain Radio Shack.

Then on top of that, get screamed at and berated by Karen the tenant because it won’t work.

 

[prcguy]

Well, I’m thinking more along the lines of the installer who is trying to put food on his table and gets screwed on his metrics and or money because some idiot at corporate said an install should only take xyz time / pay $xyz, and has to fix the previous install done by Jonny Homedepot, Larry Lowe’s and Captain Radio Shack.

Then on top of that, get screamed at and berated by Karen the tenant because it won’t work.

Don't worry about cable TV installers, they will get paid no matter what happens. Most of the time they reuse an existing system where its assumed the entire house will be wired up again. Make it the best for you, all 50 ohm if possible.

 

[cavmedic]

Don't worry about cable TV installers, they will get paid no matter what happens. Most of the time they reuse an existing system where its assumed the entire house will be wired up again. Make it the best for you, all 50 ohm if possible.

Actually not true if they are contracted installers.

 

[prcguy]

Actually not true if they are contracted installers.

There would be different pay scales for a complete new install vs just plugging in a cable box. A ham'd out wiring system would require a new install. BTW, I was a certified trainer for Sat TV installs at one time.

 

[KevinC]

Not sure why we're still taking about...or actually talking anything but the original topic...after almost one year, plus the OP hasn't visited since February. Closing.