Antenna connectors

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Phillipsc84

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OK, so I am in the process of replacing my scanner antenna and one for my dual band radio at home. My question may be nothing new but I wanted to ask. If the PL259/SO239 connectors are not great over 300MHz (likely much lower) then why are they on just about any antenna I see. Why not have N connectors on them? The radio has N, the multicoupler has N. Everything I read talks about the loss you get with "UHF" connectors and how great N is so what's the deal?

If I am asking a ridiculous question let me know. Just thought I would see what others think.
 

iMONITOR

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Actually there are many antennas available for scanner radios that use Type N connectors. What type of antenna are you looking for and for what bands/frequencies?
 

Phillipsc84

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Actually there are many antennas available for scanner radios that use Type N connectors. What type of antenna are you looking for and for what bands/frequencies?
On the scanner side something wideband. Right now it's an ancient RadioShack discone that has seen better days. Since it's feeding multiple scanners and SDR receivers it would be nice to have the customary 25-1300MHz coverage that a lot of "Scanner antennas" have. On the dual band it's a CS8000D (but may be changed out) which of course covers the majority of the 100-173MHz and 430-480MHz bands.
 

mmckenna

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If the PL259/SO239 connectors are not great over 300MHz (likely much lower) then why are they on just about any antenna I see.
That is a good question.

And the answer is that you are likely looking at scanner/hobby/amateur grade antennas. The UHF connector is popular because it's cheap and easy to install. Hobbyists like them for that.

If you look at commercial antennas, you'll see N and 7-16DIN connectors, rarely UHF connectors. There's a few other types of connector used, but N and 7-16 are the more common ones for commercial grade stuff.
 

mmckenna

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On the scanner side something wideband. Right now it's an ancient RadioShack discone that has seen better days. Since it's feeding multiple scanners and SDR receivers it would be nice to have the customary 25-1300MHz coverage that a lot of "Scanner antennas" have. On the dual band it's a CS8000D (but may be changed out) which of course covers the majority of the 100-173MHz and 430-480MHz bands.
Diamond makes a discone with an N connector. D130NJ. Reasonably priced, too. If you want to step up into higher grade antennas, there are some commercial grade discone antennas, they'll all have N connectors.

On your dual band radio, you'd get better performance if you ran a dedicated dual band 2 meter/70 centimeter antenna.
 

majoco

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There's nothing to stop you removing an SO239 socket and replacing it with an "N" chassis mount socket - except they are more expensive than the SO239 and you have to make sure that you stick to the one variety - 50 or 75 ohms.
 

iMONITOR

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On the scanner side something wideband. Right now it's an ancient RadioShack discone that has seen better days. Since it's feeding multiple scanners and SDR receivers it would be nice to have the customary 25-1300MHz coverage that a lot of "Scanner antennas" have. On the dual band it's a CS8000D (but may be changed out) which of course covers the majority of the 100-173MHz and 430-480MHz bands.
The Diamond D-130-NJ is possible the most popular wide-band scanner antenna on the market. It's a discone similar in design to what you're used to but very sturdy high quality and has the Type N connector you're looking for.

 

Phillipsc84

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Awesome responses! I like the D130NJ you mentioned. I think that will be in my future for the receive only stuff. If I'm going to potentially spend ~$845 for a 16 port multicoupler I don't want to let the antenna be the weak link. In that train of thought my antenna runs should be under 50 feet and I know LMR400 is the gold standard for feedline but is it reasonable to think I could do it with LMR240?

On your dual band radio, you'd get better performance if you ran a dedicated dual band 2 meter/70 centimeter antenna.
This is definitely my intention. I am looking over some stuff but any thoughts on this would be great too. X50NA maybe?
 

mmckenna

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Awesome responses! I like the D130NJ you mentioned. I think that will be in my future for the receive only stuff. If I'm going to potentially spend ~$845 for a 16 port multicoupler I don't want to let the antenna be the weak link.
$845 for an RX multicoupler? And you want to connect it to a $100 antenna?

In that train of thought my antenna runs should be under 50 feet and I know LMR400 is the gold standard for feedline but is it reasonable to think I could do it with LMR240?
I wouldn't ever say LMR-400 is a gold standard for anything. It's decent cable for short runs, and entirely dependent on what frequencies you are interested in. Without knowing what your area of interest is, I'd not recommend any cable. At higher frequencies, you'll want a high grade cable since the losses will increase. Since the discone has 0dB gain, you'll want all the help you can get. Again, back to the $845 coupler + $100 antenna + lower grade coaxial cable = doesn't add up.



This is definitely my intention. I am looking over some stuff but any thoughts on this would be great too. X50NA maybe?
Something along the lines of that would be good. I haven't owned one of those, so I'll avoid recommending it.
 

Phillipsc84

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$845 for an RX multicoupler? And you want to connect it to a $100 antenna?



I wouldn't ever say LMR-400 is a gold standard for anything. It's decent cable for short runs, and entirely dependent on what frequencies you are interested in. Without knowing what your area of interest is, I'd not recommend any cable. At higher frequencies, you'll want a high grade cable since the losses will increase. Since the discone has 0dB gain, you'll want all the help you can get. Again, back to the $845 coupler + $100 antenna + lower grade coaxial cable = doesn't add up.





Something along the lines of that would be good. I haven't owned one of those, so I'll avoid recommending it.
I should explain, that cost is for a Stridsberg 16 port MCA216M. It's the only one with 16 ports I have been able to find. Currently I have the ultimate cheap route of using 75ohm coax with two 8-port channelmaster drop amps to keep from losing the signal due to all the splits. It's feels messy and not ideal.

It's 14 scanners and 4 SDR receivers. The goal is to upgrade the antenna to something a little higher quality. Then split that with minimal loss to all the receivers. If there is a cheaper option for a multicoupler with at least 16 ports I am all in favor. For the discone I'm not worried at all about the transmit gain etc since it won't be a factor.

On the dual band 2m/70c it's just a straight run from radio to antenna with N connectors on both ends. That's what lead me to the X50NA. Has some gain and the right connectors and the bands the radio is in. The run is less then 50 feet and I'm ok with something like LMR400 for that since it's Rx and Tx. From my calculations @ 50feet LMR240 will have about 2-3dB of attenuation but the antenna has about 7dB of gain in the 440 band. Running a calculation at qsl.net gives this result for the LMR-240 specs.

Cable Loss per 100 ft at Operating Frequency = 5.3 dB
Cable Length = 50 Ft.
Calculated Loss = 2.7 dB
Power into Cable = 35 Watts
Power out of Cable = 19 Watts
Gain of Antenna = 7.2 dBd
ERP of Antenna System = 99.8 Watts

Sorry for the long detailed post. I appreciate all the feedback from everyone. It's helpful to throw ideas out to make sure I'm thinking in the right direction.
 

mmckenna

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I should explain, that cost is for a Stridsberg 16 port MCA216M. It's the only one with 16 ports I have been able to find. Currently I have the ultimate cheap route of using 75ohm coax with two 8-port channelmaster drop amps to keep from losing the signal due to all the splits. It's feels messy and not ideal.

It's 14 scanners and 4 SDR receivers. The goal is to upgrade the antenna to something a little higher quality. Then split that with minimal loss to all the receivers. If there is a cheaper option for a multicoupler with at least 16 ports I am all in favor. For the discone I'm not worried at all about the transmit gain etc since it won't be a factor.
Might make some sense to split things up.
Instead of 16 port multicoupler, use more than one antenna and smaller multicouplers.

Not sure what you are scanning, but it's easy to do better than a discone. If you are scanning multiple bands, a band specific antenna will easily outperform a discone. Add a patch panel, and you'd have some flexibility.

Nothing wrong with using 75Ω stuff. Yeah, there's a very slight impedance mismatch, but you'll find that your scanner and discone are not 50Ω either. A less expensive multicoupler would allow you to spend more money on the antenna system. Getting your antennas up higher and using higher grade coax will make a big difference. RG-11 is low loss….

On the dual band 2m/70c it's just a straight run from radio to antenna with N connectors on both ends. That's what lead me to the X50NA. Has some gain and the right connectors and the bands the radio is in. The run is less then 50 feet and I'm ok with something like LMR400 for that since it's Rx and Tx. From my calculations @ 50feet LMR240 will have about 2-3dB of attenuation but the antenna has about 7dB of gain in the 440 band. Running a calculation at qsl.net gives this result for the LMR-240 specs.
…...
The loss works both ways, so make sure you consider the receive side of things. If you are not trying to work a lot of simplex, then probably not a big deal and LMR-240 will work just fine. But take a look at the costs, LMR-240 vs. LMR-400, and consider that there's a considerable amount of labor and risk installing them. LMR-240 might be fine, or a higher grade cable may only add a bit of cost.

And I'd not get too hung up on the UHF vs. N connector thing. I saw your post about changing the connector on the back of the radio.
Yeah, N connectors perform better at higher frequencies, but it's really hard to hear that difference on the 440 band. Usually the small additional loss won't be heard. You'd need high end test equipment to see it.
Where the N connectors make a difference is on higher frequencies. The UHF connectors are not true 50Ω, there's a bit of an impedance bump, but you'll not notice that.
Changing out connectors to save a tenth of a dB, but running small coax doesn't seem like a good expenditure of effort in my mind. But, it's a hobby, and if you want to give it a try, go for it and let us know how it works.
There are still a lot of commercial UHF radios that have the SO-239 connectors on the back. It's not really a big deal.
 

Ubbe

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I should explain, that cost is for a Stridsberg 16 port MCA216M. It's the only one with 16 ports I have been able to find. Currently I have the ultimate cheap route of using 75ohm coax with two 8-port channelmaster drop amps to keep from losing the signal due to all the splits. It's feels messy and not ideal.
Use a low-noise amplifier at the discone and preferable a FM broadcast blocking filter. Then you can use low cost coax like RG6.

You'll need another low-noise amplifier down at the splitter. You could use splitters that have taps. From the antenna coax you could use a 6 way tap with 13dB attenuation and 4,5dB insertion loss and after that a 10dB 4-way tap with 4dB insertion loss. Then the second low-noise amp and a new set of taps choosen so that each output will have something between 0dB to 6dB gain calculated from the antenna to the receiver.

Put a power supply and the bias-T to power the antenna amp in a box and screw the splitter and taps to the outside of the box for easy access to their connectors. Make a water tight box at the antenna for the filter and amp. Sometimes they'll fit inside a discones mounting tube where they will be protected and only needs some plastic zip bags around them.

A low noise amp are probably $25-$50 each, splitters $20 each and bias-T also $20. There are different sources like Mini-Circuits and GPIOLabs. It takes a couple of hours to put together in neat boxes but you'll save hundreds of dollars and will end up with a high performance solution that will beat Stridsbergs that doesn't use any antenna amplifier to overcome coax loss that will give more system noise. See to that the amps have lower noise than NF 2dB and high IP3 like 35dBm or 40dBm.

Some examples:
Low-Noise amp
Bias-T
FM filter
Taps and splitters

/Ubbe
 

Phillipsc84

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All of this has been very helpful. To be honest I had a little too much time on my hands and probably got a little too caught up in the "PL259 over 400MHz will cost you a TON of loss" debate for my own good. I'll keep all this in mind and keep researching and see what I come up with.

Thank you to all who replied.
 

WB9YBM

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If the PL259/SO239 connectors are not great over 300MHz (likely much lower) then why are they on just about any antenna I see. Why not have N connectors on them?
When I worked in Motorola's R & D lab we used PL259/SO239 up to the cell 'phone band and at least for the stuff we were doing they worked. The only time we went to N connectors was on bands above the cell 'phone stuff. At least part of the reason is that N connectors are a major nuisance to assemble.
 

Phillipsc84

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That's good to know too. The scanners will be scanning all the way up to the 900MHz range so something that will maintain low loss all the way up there is ideally what I want.
 
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