BNC vs SMA RH77

[mpcarlino]

Hey, everyone.

This isn't so much a problem as it is curiosity, but I'm using the BNC Diamond RH77CA on my BCD396; of course using the SMA->BNC adapter. I was wondering if there's any noteworthy signal loss presented by doing this as opposed to using an SMA RH77, since I know that any type of adapter presents some signal loss; I'm just wondering how much. I'm very impressed with its performance, but I was considering ordering another RH77 as a spare/backup. If there's a large enough difference, I'd probably order an SMA version and use the BNC version as a spare.

It's easier to switch between my discone and the RH77 using the BNC adapter, so I might not change anything, following the "if it ain't broke, don't fix it" philosophy. After all, most other handheld scanners/receives use BNC. Like I said, just curiosity.

Thanks.

 

[N4JNW]

You're right. Anytime you use an adapter, or something, then there will be a small amount of signal loss.

But, since the "hard" connections are still made, it isn't going to be significant. You couldn't measure it really. As long as the antenna's center pin and ground are in good contact, everything will be fine.

 

[mpcarlino]

Sounds good. That's what I suspected, but I needed a more expert opinion than my own. My 396 performed superbly with the RH77 at this weekend's airshow in Niagara Falls; both at the base and from my house 20 miles away in the backyard. It's definitely my antenna of choice for handhelds.

I think my real weakest link is the coax with my indoor discone. I'm using 12' of RG58 that I purchased at RS a few years ago. I know that type of coax is crap in general, but does it make a big difference at 12'? Not to get away from the topic at hand, of course.

Thanks for your reply!

 

[N4JNW]

I'll agree with you. The RH77CA is a real performer on aircraft, VHF and UHF. I really like mine. I wouldn't mind having another.

As far as your coax goes, RG58 is good for lower frequencies, as it's most commonly used for CB radio application. At higher frequencies, it usually becomes quite lossy. Even with 12' of it. I've always told folks, your coax is your lifeline. You can have the biggest, best scanner in the world, and the biggest antenna outside, but if your coax isn't quality, you won't recieve jack.

A good antenna, and good coax will make a 30 year old crystal type scanner scan circles around a Bearcat 996 with a poor antenna system.

Although it IS quite pricey, I reccomend LMR400. It's quite popular for a reason.

 

[oceans777]

I have both the BNC and SMA RH77CA and have 'tested' the difference by using the SMA version on my BCD396T to lock in a faint, distant airport ATIS signal and then switch to the BNC with the adapter. Absolutely no discernible difference. I've tried it using a variety of weaker signals and either antenna yielded the same reception.

There probably is some loss with the adapter but it's around 1.1 dB and probably the least factor in reception.

12' of RG58 is not going to be a serious problem either - I think you probably lose about 2 dB at 1200 MHz which is ok. Moving the discone outside and as high as you can within reason is always the best idea and if you did that it would be worth investing in better coax if you ran around 25 feet or more. Many people use them in attics with good results too though.

Coax loss is always a well debated topic - some want nothing but LMR400 or hardline and hate any loss while others prefer to trade off flexibility, ease of coax handling and lower cost for a little more loss.
I personally it's worth getting the best coax you reasonably can - why spend $500 on the latest receivers and then lose signal if you don't have to?
And once you do hear the difference in reception something like LMR400 can make it's hard to ever go back...

Here's a general coax loss calculator you can use - just ignore power and SWR for receive only.

http://www.ocarc.ca/coax.htm