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Grogster
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Posted: 28 November 2017 at 11:50am | IP Logged Quote Grogster

Does anyone know where I can get an amplified splitter for 458MHz or so?
Receive only, no transmit path used or required.

I have a roof-mounted antenna, tuned for 458MHz, currently feeding one singular receiver unit. I want to use the same antenna to receive signals for THAT system, and also to pick up signals transmitted on an adjacent channel frequency.

My first thought was a passive TV splitter, as they are supposed to be broadband up to about 2GHz, but the only problem with a passive split, is that you lose 3dB(half) of your input signal across the split, and that makes that approach unattractive, as taking 3dB off the receive sensitivity could result in failure of one receiver to see the signals from far away nodes.

The next thing I thought of was perhaps a simple TV booster amplifier such as this thing here from Jaycar, which has variable VHF and UHF controls, so set VHF to minimum, and UHF to minimum also - or around 3dB-ish gain, and put a passive split after that.

Does anyone see any issue with that idea, or perhaps do any of the members here know of a special type of active splitter concept I can use in this situation?

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Boppa
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Posted: 28 November 2017 at 1:48pm | IP Logged Quote Boppa

Jaycar used to have an amplified tv splitter similar to the above but with dual outputs, I got 3 of them here atm, Ill take a pic of the model number

Or just use a masthead amp with dual outputs? (depends where you want the split to go to)



Edited by Boppa on 28 November 2017 at 1:50pm
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Posted: 28 November 2017 at 2:01pm | IP Logged Quote Boppa

These are the ones, had a lot of good use out of them over the years, I got some through jaycar, others through bunnings





Latest one I bought was about 18 months ago for the tv I used in the 4x4 for camping, cost around $40

Cant find them on either of their online cattledogs, ebay has one
http://www.ebay.com.au/itm/DIGITAL-TV-SIGNAL-BOOSTER-AMPLIFIER-KINGRAY-SA162F/200782447030?epid=17003301376&hash=item2eb f9101b6:g:U5cAAOSwC8FZcBJV

I can see other brands out there, just I had a lot of issues where I was living with lightning, lost lots of masthead amps to thunderstorms, found these to be quite immune to them compared to other brands

Edited by Boppa on 28 November 2017 at 2:10pm
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Grogster
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Posted: 28 November 2017 at 2:09pm | IP Logged Quote Grogster

Yes, the good 'ole Kingray SA162 - I know it well.

It does not have any kind of gain control though, so my thoughts were that it might overload things more then it helps. Not sure though. I will have a look for one of those, as I am sure I have at least a couple myself.

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Posted: 28 November 2017 at 2:17pm | IP Logged Quote Boppa

A remarkably good lil unit arent they, I havent had one failure in years, and I put a lot of them in
Actually I tell a lie, I did have one failure, due to cat urine LOL- pussycat was in the habit of sleeping on the warm vcr and had an accident, vcr failed, amp splitter failed and tv failed all within 6 months...
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Posted: 28 November 2017 at 2:22pm | IP Logged Quote Boppa

Hmm the 164 (4 way outputs) version has a gain control adjustable by a small screwdriver
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skyv
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Posted: 28 November 2017 at 4:49pm | IP Logged Quote skyv

Radio Part have a few offerings


http://www.radioparts.com.au/category/tv-antenna-systems/tv-antenna-access/splitter-amps


skyv
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Posted: 29 November 2017 at 6:06am | IP Logged Quote Phil23

This one is 435 Meg.

Wonder if it's re-tunable by changing a few components.

Might be others that are more suitable.

Phil.

Edit:-

Seems from the description it can be reconfigured...

IE,





Edited by Phil23 on 29 November 2017 at 6:10am
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Grogster
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Posted: 29 November 2017 at 7:20am | IP Logged Quote Grogster

Thanks skyv and Phil.

I have enquired with the Aliexpress seller if their amp can be adjusted to 458MHz.
That would be an ideal solution, coupled into a standard tw-way passive splitter, with each output port feeding a receiver. With a amp gain of 3dB + whatever insertion loss of the amp itself, each receiver should see the same signal level as the original antenna and receiver.

I like the Aliexpress unit, as being band-pass, it will have nice attenuation on all other frequencies - a channelised amplifier, as I used to call them.

A broadband amp would probably work I expect, but being broadband, the amp could also pass through a lot of other spectrum noise which might swamp the receiver if you see where I am coming from. RF is fun, isn't it! (rhetorical!)

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Posted: 29 November 2017 at 2:44pm | IP Logged Quote kg4pid

Have you tried using the splitter without any additional amplification? In the grand scheme of things 3db isn't much. If the splitter does affect the signal, then it was marginal to begin with. Your coax could easily have that much loss and more at that frequency depending on type and length. A TV splitter will be 75 ohm, what is your antenna and coax rated for? Mixing 50 ohm and 75 ohm will also cause minor losses.

Max
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Grogster
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Posted: 29 November 2017 at 4:58pm | IP Logged Quote Grogster

Good points! The ant and receiver are 50-ohm, but any TV splitter will be 75-ohm.
Just HOW much can I expect that to alter things?
I do indeed plan to do some site tests before anything else.

Edited by Grogster on 29 November 2017 at 5:03pm


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Posted: 29 November 2017 at 6:34pm | IP Logged Quote palcal

Hi Grogs, what about a scanner antenna splitter, it would be 50 ohm. 458MHz is just below the scanner frequencies that I think start about 460 MHz.
Paul.

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