RECEIVERS
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Message from PaulD at Wednesday, 27-Jan-10 12:37:38 GMT
OK. here's the plan.
My NOAA receiver, and Hope to get an old scanner on 145.8 FM for picking up ISS. Is there an issue in hooking up the 2 scanners to 1 antenna? Was thinking of maybe using similar to a TV Signal Booster. or a Y Junction. Have you any ideas? Be interested in feedback.
/Paul D
My NOAA receiver, and Hope to get an old scanner on 145.8 FM for picking up ISS. Is there an issue in hooking up the 2 scanners to 1 antenna? Was thinking of maybe using similar to a TV Signal Booster. or a Y Junction. Have you any ideas? Be interested in feedback.
/Paul D
Message from Calico at Wednesday, 27-Jan-10 13:21:55 GMT
You are looking for a splitter.
Mini-circuits, etc manufacture them.
Look up eBay for "splitter" and or "combiner" or Google for new.
Various specs for various budgets, if you want port isolation look for more than 100 quid
Tim
Mini-circuits, etc manufacture them.
Look up eBay for "splitter" and or "combiner" or Google for new.
Various specs for various budgets, if you want port isolation look for more than 100 quid
Tim
Message from PaulD at Wednesday, 27-Jan-10 13:59:26 GMT
Is there a specific one i need? Is there an Item no. or link I can look at?
/Paul
It is only going to receive on 137 and 145 FM
Last edited by PaulD at Wednesday, 27-Jan-10 14:43:17 UTC
/Paul
It is only going to receive on 137 and 145 FM
Last edited by PaulD at Wednesday, 27-Jan-10 14:43:17 UTC
Message from Calico at Wednesday, 27-Jan-10 14:53:52 GMT
So as not to limit your future prospects, maybe a wider range would be better and one way or another splitters don't come in such narrow range (<10 MHz)
Here is a quite good specs splitter with 50 dB typical isolation and importantly 50 Ohm inmpedance and freq range from 0 kHz to 4.6 GHz.
Its specs at: http://www.minicircuits.com/pdfs/ZFSWA-2-46.pdf
Someone selling it on ebay item # 110478565262
Have a look maybe for BNC connector type though,don't know your connectors.
Avoid TV splitters, e.g. "Y-splitters" etc, they are wrong impedance and toys rather than tools
Here is a quite good specs splitter with 50 dB typical isolation and importantly 50 Ohm inmpedance and freq range from 0 kHz to 4.6 GHz.
Its specs at: http://www.minicircuits.com/pdfs/ZFSWA-2-46.pdf
Someone selling it on ebay item # 110478565262
Have a look maybe for BNC connector type though,don't know your connectors.
Avoid TV splitters, e.g. "Y-splitters" etc, they are wrong impedance and toys rather than tools
Message from PaulD at Wednesday, 27-Jan-10 15:45:13 GMT
Ok Thanks Tim, Will have a play.
/Paul D
/Paul D
Message from Calico at Thursday, 28-Jan-10 02:30:59 GMT
No worries
Tim
Tim
Message from iz0mvn at Sunday, 31-Jan-10 10:01:58 GMT
Hi Paul,
1) in RX operations you can try a simple "T";
2) you can try also a "hibrid coupler" 3 ports, or 4 ports (1 adapted).
3) you can use a band-pass/band-stop filter (like duplexer).
'73 Aki
1) in RX operations you can try a simple "T";
2) you can try also a "hibrid coupler" 3 ports, or 4 ports (1 adapted).
3) you can use a band-pass/band-stop filter (like duplexer).
'73 Aki
Message from AceB at Sunday, 31-Jan-10 13:06:31 GMT
I use a small Maxview TV distribution amp to feed one antenna to half a dozen different rx's with no problems. I've done numerous tests to test for intermodulation, overload and signal degradation and found none, even on AIS decoding. The only time it does suffer is when the ham about 300m away fires up on 2m. The difference in impedance doesn't really effect anything on receive.
Message from Calico at Monday, 01-Feb-10 01:11:47 GMT
Serious radio designs and testing labs go to great lengths to isolate port "leaks". Signals can leak from one antenna port to the other, .
The higher the isolation between ports of a splitter, the higher the quality of the splitter. Since most receivers leak signals from port to port, isolation of more than /40 dB/ (using absolute figures) is necessary if not more.
If a radio does not have a second port e.g. Icom PCR-1000 by design, and we forcefully introduce a second port by means of a cheap or irrelevant "splitter" connected to a second radio then we open the door to the other radio "leaking" all sort of unwanted signals to one another, from mixers to local isolators etc of both radios interacting with one another.
Some years ago in London, I was comparing the performance of a TenTec OMNI-VI with a friend's TenTec Paragon. Products and problems appeared when the two radios were connected to the same antenna via a cheap inexpensive combining device. Linearity was lost, and what should appear on some standard frequencies (e.g. WWV's 15 000 kHz) appeared on the wrong frequency (i.e. 15 004 kHz). Specific frequencies became noisier, resulting into signals now being buried into noise. Took some head scratching to reject (bin) the el-cheapo combining device than rejecting the newly bought (and expensive) radio.
RF-Systems make one of the best (active) receiving antennas in the world, the DX Pro I. It's not accidental that when they combine two radios to this same expensive antenna 40 dB isolation over the *entire* 0.1-30 MHz range is used.
In their own words:
The RF Systems DX-One Professional MkII rear panel features two-isolated receiver outputs (SO239 type).
This permits the simultaneous feed of up to two receivers with *no interaction or interference between the two radios*.
America's ARRL, WRTH, RSGB and any serious organisation/lab, etc would not dream of testing without a proper splitter with high (if not variable) port isolation. They regard port isolation as *critical* for hearing what comes from the antenna rather than what comes from ..another radio!
"The port-to-port isolation of the two port combiner is critical to the accuracy of the test results"(Source: ARRL Technical Department Laboratory, QST Product Review, Serial: 01A10087, Centaur)
"At 14 MHz, if the coupler is properly terminated in a 50 Ohm load, the Mini Circuits coupler we used offers a measured isolation of > 35 dB, which combined with the generator's attenuation results in an isolation of > 75 dB between the two output ports".
Source (Swept Receiver Dynamic Range Testing in the ARRL Laboratory)
RF-Systems DA-4, 4 way Distribution Amplifier / Aerial Multicoupler
offers > 125 dB dynamic range, and over 30 dB isolation between receivers (all and each of the 4 receivers it can feed). Quality of course costs, 352.00 Euro for just a splitter.
For Paul's and our practical needs, in addition to proper isolation (the higher dB the better), a good splitter needs to also maintain impedance symmetry between any number of ports. Not only do we need the one port not to leak "products" to the other port, but also to ensure that the splitter will maintain -no matter what!- the 50 Ohm impedance, constant throughout the entire specified frequency spectrum despite if the load (e.g. is 50 Ohm at 3 MHz or 397 Ohm at 8 MHz.)
TV distribution amplifiers are OK for TVs and devices that have similar frequency / input circuit characteristics to "TVs".
However and with all the due respect to "AceB":
1) They are for VHF/UHF and not designed for coexisting with HF circuits.
2) They provide no whatsoever port isolation between radios.
3) They deviate by 50% (!) off the 50 Ohm input impedance of most multiband radios, including of course the Icom PCR-1000.
4) Since a splitter can be used as a combiner, we may decide to use the same device to combine two antennas (e.g. a discone for V/U and a high-gain MF/HF) and feed one radio. But then the one (MF/HF) antenna may overload the input (e.g. of any scanner) with huge signals. Hence we need to consider not only isolating radio ports but also the one antenna from the other before they reach the radio, e.g. by some HPF/LPF circuit. :- )
Andy Ikin, the man who made both mine (many years ago) and Paul's Wellbrook ALA-1530 makes and sells an excellent splitter for 100 kHz to 30 MHz providing port isolation of a descent 25 dB between each of the 4 ports and about 8dB gain too! (Wellbrook AS1030)
And quality, doesn’t come cheap, this splitter costs £180.00, a "bargain" compared to the one by RF-Systems.
But even at this cost, to ensure this isolation, a 50 Ohm termination load needs to be fitted to any unused ports, which is the right operational practice with any splitter one way or another.
Ten-Tec makes a great splitter, 651 Isoline, that maintains port-to-port isolation of >50 dB over any 30-MHz of bandwidth within most of its range of 2-300 MHz!
If one uses a cheap “toy-splitter” they may well be, "happily ignorant" of the performance degradation.
It would take a proper A/B test between a proper splitter and a "toy-splitter" and at least a good spectrum analyser to see the differences and get them to “bin” the toy for a proper “broadband” splitter.
After all, as everyone knows, RF signals will follow the path of least resistance.
But the "path of least resistance" for what price we pay for a splitter, may make monitoring frequencies become a waste of time, if not a waste of money as well.
The higher the isolation between ports of a splitter, the higher the quality of the splitter. Since most receivers leak signals from port to port, isolation of more than /40 dB/ (using absolute figures) is necessary if not more.
If a radio does not have a second port e.g. Icom PCR-1000 by design, and we forcefully introduce a second port by means of a cheap or irrelevant "splitter" connected to a second radio then we open the door to the other radio "leaking" all sort of unwanted signals to one another, from mixers to local isolators etc of both radios interacting with one another.
Some years ago in London, I was comparing the performance of a TenTec OMNI-VI with a friend's TenTec Paragon. Products and problems appeared when the two radios were connected to the same antenna via a cheap inexpensive combining device. Linearity was lost, and what should appear on some standard frequencies (e.g. WWV's 15 000 kHz) appeared on the wrong frequency (i.e. 15 004 kHz). Specific frequencies became noisier, resulting into signals now being buried into noise. Took some head scratching to reject (bin) the el-cheapo combining device than rejecting the newly bought (and expensive) radio.
RF-Systems make one of the best (active) receiving antennas in the world, the DX Pro I. It's not accidental that when they combine two radios to this same expensive antenna 40 dB isolation over the *entire* 0.1-30 MHz range is used.
In their own words:
The RF Systems DX-One Professional MkII rear panel features two-isolated receiver outputs (SO239 type).
This permits the simultaneous feed of up to two receivers with *no interaction or interference between the two radios*.
America's ARRL, WRTH, RSGB and any serious organisation/lab, etc would not dream of testing without a proper splitter with high (if not variable) port isolation. They regard port isolation as *critical* for hearing what comes from the antenna rather than what comes from ..another radio!
"The port-to-port isolation of the two port combiner is critical to the accuracy of the test results"(Source: ARRL Technical Department Laboratory, QST Product Review, Serial: 01A10087, Centaur)
"At 14 MHz, if the coupler is properly terminated in a 50 Ohm load, the Mini Circuits coupler we used offers a measured isolation of > 35 dB, which combined with the generator's attenuation results in an isolation of > 75 dB between the two output ports".
Source (Swept Receiver Dynamic Range Testing in the ARRL Laboratory)
RF-Systems DA-4, 4 way Distribution Amplifier / Aerial Multicoupler
offers > 125 dB dynamic range, and over 30 dB isolation between receivers (all and each of the 4 receivers it can feed). Quality of course costs, 352.00 Euro for just a splitter.
For Paul's and our practical needs, in addition to proper isolation (the higher dB the better), a good splitter needs to also maintain impedance symmetry between any number of ports. Not only do we need the one port not to leak "products" to the other port, but also to ensure that the splitter will maintain -no matter what!- the 50 Ohm impedance, constant throughout the entire specified frequency spectrum despite if the load (e.g. is 50 Ohm at 3 MHz or 397 Ohm at 8 MHz.)
TV distribution amplifiers are OK for TVs and devices that have similar frequency / input circuit characteristics to "TVs".
However and with all the due respect to "AceB":
1) They are for VHF/UHF and not designed for coexisting with HF circuits.
2) They provide no whatsoever port isolation between radios.
3) They deviate by 50% (!) off the 50 Ohm input impedance of most multiband radios, including of course the Icom PCR-1000.
4) Since a splitter can be used as a combiner, we may decide to use the same device to combine two antennas (e.g. a discone for V/U and a high-gain MF/HF) and feed one radio. But then the one (MF/HF) antenna may overload the input (e.g. of any scanner) with huge signals. Hence we need to consider not only isolating radio ports but also the one antenna from the other before they reach the radio, e.g. by some HPF/LPF circuit. :- )
Andy Ikin, the man who made both mine (many years ago) and Paul's Wellbrook ALA-1530 makes and sells an excellent splitter for 100 kHz to 30 MHz providing port isolation of a descent 25 dB between each of the 4 ports and about 8dB gain too! (Wellbrook AS1030)
And quality, doesn’t come cheap, this splitter costs £180.00, a "bargain" compared to the one by RF-Systems.
But even at this cost, to ensure this isolation, a 50 Ohm termination load needs to be fitted to any unused ports, which is the right operational practice with any splitter one way or another.
Ten-Tec makes a great splitter, 651 Isoline, that maintains port-to-port isolation of >50 dB over any 30-MHz of bandwidth within most of its range of 2-300 MHz!
If one uses a cheap “toy-splitter” they may well be, "happily ignorant" of the performance degradation.
It would take a proper A/B test between a proper splitter and a "toy-splitter" and at least a good spectrum analyser to see the differences and get them to “bin” the toy for a proper “broadband” splitter.
After all, as everyone knows, RF signals will follow the path of least resistance.
But the "path of least resistance" for what price we pay for a splitter, may make monitoring frequencies become a waste of time, if not a waste of money as well.
Message from Calico at Monday, 01-Feb-10 01:20:12 GMT
Why ARRL use high-end splitters (e.g. TenTec's IsoLine 651) and what proper A/B procedures are like can be seen at the "Test Procedure Manual" a juicy 159-page document, to be found at:
http://p1k.arrl.org/~ehare/testproc/testproc.pdf
http://p1k.arrl.org/~ehare/testproc/testproc.pdf
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