Single Splitter with both RG-6 and RG-59 connections

[Comptech]

Hey, not trying to be rude, but with your book smarts and common sense dumb, I could start a thread about how great RG59 is and the first thing you would post is you would be you would be better off using quality RG6.

 

[Comptech]

The frequency range we're discussing tops out at 608MHz.

Signal loss in an RF impedance mismatch situation comes from some percentage of the signal being reflected back at the load in addition to the normal distance attenuation. This Stack Exchange article presents the formula for reflection:

Impedance mismatch vs Signal attenuation

I'm currently designing a 50Ω grounded coplanar waveguide (GCPW) which connects an antenna to an LTE modem. My question is: does there exist a standard graph/chart that attempts to generalise imped...

electronics.stackexchange.com

The result is that no matter what you do with the cable and its connectors (outside of baluns and amplfiers), the scanner is ultimately going to bounce back 0.177dB of the signal back into the cabling network. It isn't much, but what is there is all bad.

When people use splitters with a 3 Db loss and work fine, Are you serous with your, point 07 db loss? And what load? We are talking about receive. You are much more about showing off than reading a forum and understanding the question, again, book smart, common sense dumb.

 

[harshness]

The difference being that this "loss" is really a reflection which introduces something different and even more undesirable than a reduced signal. The harmonics may or may not rise to the level of a problem.

 

[Don in CT]

Hey, not trying to be rude, but with your book smarts and common sense dumb, I could start a thread about how great RG59 is and the first thing you would post is you would be you would be better off using quality RG6.

What is the advantage of using RG59?

 

[harshness]

What is the advantage of using RG59?

A smaller bend radius is perhaps the best reason.

 

[Don in CT]

A smaller bend radius is perhaps the best reason.

That can’t be much of a difference. You can’t bend any coax to far before it kinks.

 

[harshness]

That can’t be much of a difference. You can’t bend any coax to far before it kinks.

The RG59 minimum bend radius is around 1.2" versus RG6 which is around 2.5 - 4" depending on how many shield layers there are. RG11 cable starts at around 4.5" minimum bend radius.

 

[Titanium]

You guys must love posting on QRZ.... LOL

Op asks how deep is the ocean is and the thread turns into an aurgument over the color of the sky...

 

[Comptech]

Hell you could get a bad crimp on Lmr 400 and never notice the ohm mismatch on a receive only setup.

 

[Comptech]

None that I am aware of.

What is the advantage of using RG59?

Good quality RG6 solid copper swept to 3 gigs will work fine on any receive application. Cheap easy and effective.

 

[Tower Guy]

A response to the original question

Hello all,

I have an existing RG-6 cable run for a VHF antenna and radio system. My co-worker has a VHF scanner that accepts a RG-59 bnc connection. Is there a way to split the RG-6 cable and run a RG-59 cable from the existing cable run? Like a splitter with both RG-6/59 connections in one? Or am I going to have to run an entirely new RG-59 cable? Any input is greatly appreciated

The suggestion that you use a type F to BNC adapter and a 75 ohm 2-way TV splitter is the easiest solution. That however, does not address antenna polarization differences between TV and two-way. A Horizontally polarized TV antenna will not be efficient picking up Vertically polarized two-way radio. Also, some TV antennas are not designed for VHF reception, which includes the VHF two-way band. Yet, if the two way signals are local, it may work OK for you anyway.

 

[Inclined Orbit]

There 100's of people on Radio Reference that would love to have a conversation about it with you.

Maximum power transfer will only happen when the impedance is matched. A 50 to 75 ohm mismatch in a purely resistive world is not that bad, something around .4dB. However, coax does not live in a resistive world and the length 50 ohm coax attached to a 75 ohm system or vice versa can have more or less loss due to the impedance transformation effects from critical lengths of wrong cables. When connecting a different impedance coax to a splitter it will usually cause an amount of amplitude ripple throughout the splitter on all its related outputs. Its always best to not mix different impedance cables.

Yes on the TV antenna being horizontally polarized and most anything you would receive on a police scanner would be vertically polarized plus TV antennas are not designed to cover public service or amateur frequencies, they skip over them except for the very cheapest stuff out there which probably doesn't work so good on TV frequencies anyway.

Loss is loss regardless if its a transmit or receive function. You won't notice a small amount of loss like less than 1dB on a police scanner connected to a TV antenna but on a fine tuned weak signal amateur setup, absolutely. Try talking your way out of a new $1mil satellite uplink antenna install that doesn't meet G/T specs buy just 1dB. Nobody gets paid until that 1dB is found and fixed. Been there and done that way too many times.

Most of the discussion in this thread is about compromise. Unnecessary loss in an RF system is compromise and everyone will have a different opinion of how much is acceptable. For me personally you can probably see its a big deal but for others not so much.

 

[Comptech]

Maximum power transfer will only happen when the impedance is matched. A 50 to 75 ohm mismatch in a purely resistive world is not that bad, something around .4dB. However, coax does not live in a resistive world and the length 50 ohm coax attached to a 75 ohm system or vice versa can have more or less loss due to the impedance transformation effects from critical lengths of wrong cables. When connecting a different impedance coax to a splitter it will usually cause an amount of amplitude ripple throughout the splitter on all its related outputs. Its always best to not mix different impedance cables.

Yes on the TV antenna being horizontally polarized and most anything you would receive on a police scanner would be vertically polarized plus TV antennas are not designed to cover public service or amateur frequencies, they skip over them except for the very cheapest stuff out there which probably doesn't work so good on TV frequencies anyway.

Loss is loss regardless if its a transmit or receive function. You won't notice a small amount of loss like less than 1dB on a police scanner connected to a TV antenna but on a fine tuned weak signal amateur setup, absolutely. Try talking your way out of a new $1mil satellite uplink antenna install that doesn't meet G/T specs buy just 1dB. Nobody gets paid until that 1dB is found and fixed. Been there and done that way too many times.

Most of the discussion in this thread is about compromise. Unnecessary loss in an RF system is compromise and everyone will have a different opinion of how much is acceptable. For me personally you can probably see its a big deal but for others not so much.

And here I thought this was recieve only situation for a scanner. Thank you for the input. A vhf high/Uhf antenna flipped on it's side will work fine with a scanner on Rg6.

 

[Comptech]

I would like you antenna pro's to explain how I bougt the antenna craft yagi 91, I t under my front porch not mounted on a pole yet and I get my local VHF low station 40 miles away on real channel 2 and it is pointed 180 degrees from their tower with the backside of the antenna blocked by the house? Theory and real world are two different things.

 

[Comptech]

I have mountains to the north, maybe reflecting back at me? but how could a antenna with such short elements possibly pick that vhf low channel. Just waiting for the experts to answer.

 

[Inclined Orbit]

And here I thought this was recieve only situation for a scanner. Thank you for the input. A vhf high/Uhf antenna flipped on it's side will work fine with a scanner on Rg6.

"A vhf high/Uhf antenna flipped on it's side will work fine with a scanner on Rg6". I would ask, compared to what? That is a key question that anyone should ask when hearing reviews on antennas or information that doesn't sound quite right. A TV antenna on a roof feeding a police scanner in the basement with RG6 will almost always work better than the supplied rubber duck antenna on the scanner in the basement. But it will be down in performance compared to a known good scanner antenna and you will have to turn it with a rotor if signals are coming from different directions, not something I would recommend for the average scanner user.

A VHF/UHF TV antenna compared to a good omni vertical polarized scanner antenna can be a night and day difference in favor of the scanner antenna. I've done lots of A/B tests on this and there is stuff you will not pick up with the TV antenna that you will with the dedicated scanner antenna, unless its a failed design, which unfortunately some are. Antennas are my thing and I probably test more communications antennas in some busy months than most people will encounter in their lifetime.

Getting back to my "compared to what?" statement, I see lots of antenna reviews where someone claims this is the best antenna out there because right out of the box they talked to Japan and Europe on it. Turns out its the only antenna they have ever used and they picked the bottom of the barrel, worst on the market but happened to hit some good propagation that week. In reality a wet noodle would have worked as well but since its the only antenna the reviewer ever owned or used its the best they ever used. Eham and QRZ are full of these false positive reviews with nothing to back them up.

So a TV antenna, not even turned on its side will receive stuff, I think we all know that. Is it the right antenna to recommend for police scanner use? Absolutely not, so why would you recommend it? It would be like me saying, to align your DirecTV dish just peak it on any Ka transponder and it will be good to go. Installers and people familiar with the dish and alignment procedure would cringe if I were to post that as the thing to do, but the uninformed may not know any better and take that advice. You have to be careful what you post and good or bad, I'm real adamant about posting correct information whenever possible so people don't waste time and money due to some bad info.

 

[Inclined Orbit]

I have mountains to the north, maybe reflecting back at me? but how could a antenna with such short elements possibly pick that vhf low channel. Just waiting for the experts to answer.

Obviously there is enough field strength in your area for it to pick up enough signal on an antenna that is not resonant to at least meet the minimum SNR needed by your receiver. A log periodic TV antenna will usually have very poor F/B ratio on its lowest frequency elements and especially if its receiving a frequency way lower than its low end cutoff, meaning it can pick up just fine off the back side. If its a cut to frequency VHF high band Yagi, the reflector will be way too small to give much of any F/B ratio at a much lower frequency that what its designed for, so if the field strength is adequate for the dipole feed elements to pick up a useable SNR, the reflector side aimed at the station might as well not even be there if its cut for VHF hi band and your receiving ch 2 in the 50MHz range.

Last year I helped install a new TV transmitter and feedline for the rapack where a station went from a UHF channel with about a 14dBi gain omni and 20kW to ch 5 VHF with maybe 6dBi gain antenna and only 10kW. At about 65mi away I pick them up just fine on my VHF high band/UHF TV antenna that is 90 deg to the now ch 5 station that my antenna doesn't cover. If the field strength meets the minimum requirements, you got a picture.

 

[Comptech]

Thank you, you just proved a UHF antenna can pick up VHF low. Blows the can't be done out the window. Trial and error are the best tools. Do what works for you, but don't blow of any comment that says that won't work. In theory you are correct, but in real world situations things are different. Again, not being rude, but look at my post in the OTA section, I was combing antennas when I got this one I just run it solo after running combined, It picks up more. Antenna theory is just that theory. Now on transmit it is a different animal.

 

[Comptech]

Silicone dust says 94 percent on the vhf channel 2, you explain to me. I will submit a picture of the antenna sitting under my porch roof sitting on a dog house if needed. I get 70 channels in that configuration. More metal more signal.

 

[harshness]

Silicone dust says 94 percent on the vhf channel 2, you explain to me.

Silicon (not cone) Dust's tuners make good use of Automatic Gain Control. A good weak signal can be better than a strong one that has interference.