SDS200 with/without Stridsberg

[samcken]

Background - I had a 4 port MCA204M feeding 4 scanners from a discone. I got a second antenna more sensitive to frequencies I wanted to monitor, and fed the multi-coupler with that. I dropped the SDS200 feed from the Stridsberg, and fed it directly from the discone, using the same wiring that used to feed the Stridsberg. It was my belief that there was no gain from either the discone or the Stridsberg. Now my question - since putting the sds200 directly on the discone, simulcast performance seems to have declined slightly (at rare times it sounds like simulcast issues which I never had before). Received volumes also seem to be louder or softer than they used to be. I will be dropping talk groups for a nearby town because while dispatch is still loud and clear, several units are almost inaudible. Over all I still get satisfactory performance, but I am puzzled about the change, since I thought there would be no change in signal gain. What did I overlook?

 

[escortz28]

Background - I had a 4 port MCA204M feeding 4 scanners from a discone. I got a second antenna more sensitive to frequencies I wanted to monitor, and fed the multi-coupler with that. I dropped the SDS200 feed from the Stridsberg, and fed it directly from the discone, using the same wiring that used to feed the Stridsberg. It was my belief that there was no gain from either the discone or the Stridsberg. Now my question - since putting the sds200 directly on the discone, simulcast performance seems to have declined slightly (at rare times it sounds like simulcast issues which I never had before). Received volumes also seem to be louder or softer than they used to be. I will be dropping talk groups for a nearby town because while dispatch is still loud and clear, several units are almost inaudible. Over all I still get satisfactory performance, but I am puzzled about the change, since I thought there would be no change in signal gain. What did I overlook?

I have and use several Stridsberg multicouplers including the MCA204M. Depending on the frequency, the multicoupler can have up to +2dB gain. Appears from the Stridsberg gain vs frequency graph that 700-800 MHz is ~+2dB gain.

 

[rf_patriot200]

If I remember correctly, Stridsberg claimed a 10db distribution amp in the specs of my MCA204 MIL

 

[buddrousa]

Specifications: MCA204M, MCA204MIL and MCA202M
Frequency Range: 25 MHz to 1 GHz 4-Ports
Nominal Impedance: 50 ohm
Port-To-Port isolation (min): 22 dB
Return Loss (all ports): > 20 dB
P1dB = 17 dBm (output) 3OIP = 32 dBm (output
Coupler Gain/Loss: +2 dB to -1 dB (max) over frequency range
RF Connectors: BNC (standard)
Mechanical: 4.375 X 2.375 X 1.250 inches (L.W.H)
Case: Die cast Aluminum, Black powder coating (standard)
DC Power Connector: 2.1/5.5mm coaxial (standard)
DC ower Requirements: +12VDC (nominal) @ 85 mA

 

[Ubbe]

What signal levels in dBm do you see? What happens if you switch the antenna and scanner back as it was, it's BNC so would be easy to do?
Configure the display to show data bit errors and you'll see in plain numbers if you get a worse digital reception. Then check with different filter settings in your scanner if you can lower the bit errors.

Stridsberg have some gain but also have a higher noise figure than what the gain compensates for, so logically you should get a better reception without the Stridsberg inline. But SDS scanner doesn't like big signals and works better when receiving lower level RF signals.

/Ubbe

 

[rf_patriot200]

What signal levels in dBm do you see? What happens if you switch the antenna and scanner back as it was, it's BNC so would be easy to do?
Configure the display to show data bit errors and you'll see in plain numbers if you get a worse digital reception. Then check with different filter settings in your scanner if you can lower the bit errors.

Stridsberg have some gain but also have a higher noise figure than what the gain compensates for, so logically you should get a better reception without the Stridsberg inline. But SDS scanner doesn't like big signals and works better when receiving lower level RF signals.

/Ubbe

My closest Starcom tower is less than a mile, but using a tower 30miles away, my error rate goes up 3-5 without the Stridsberg inline.

 

[Ubbe]

My closest Starcom tower is less than a mile, but using a tower 30miles away, my error rate goes up 3-5 without the Stridsberg inline.

What does the dBm value show with and without the Stridsberg? A higher value could indicate a detection of more RF interference as SDS scanners measures RF levels over a wider spectrum.

/Ubbe

 

[rf_patriot200]

What does the dBm value show with and without the Stridsberg? A higher value could indicate a detection of more RF interference as SDS scanners measures RF levels over a wider spectrum.

/Ubbe

My dbm reading is about 40-45 with the Stridsberg and about in 80's to 115dbm without it inline.

 

[Ubbe]

It should only be a couple of dB's in difference and not 40dB. That's a 10,000 difference in level that are the result from how the SDS scanner operates and functions in relation to interference and overload issues. If you have the waterfall feature you can probably see more clearly whats' going on in the receiver.

A tower 30 miles away should not get you a -40dBm signal and a -80dBm reading seems more realistic.

/Ubbe

 

[buddrousa]

30 miles I see a TACN Site I see -91Db to -98Db through my Stridesberg setup.

 

[N9JIG]

Sometimes anecdotal evidence is more telling than scientific. For example, I recently put up a new antenna and tested it while directly connected to both my R8600 and then a few Uniden scanners (SDS200's, 536's) using weather channels as subjects With the Stridsberg I am hearing 4 different stations of varying distances, 2 of which are very noisy. With the exact same setup but with the radios connected thru an 8-port active Stridsberg MC I am now hearing an additional weather channel 130 miles away and full quieting on the new one and both of the formerly weak ones.

I have noticed however that the noise floor displayed on the R8600 increased somewhat with the multicoupler but it did not require any increase in the squelch control.

 

[rf_patriot200]

It should only be a couple of dB's in difference and not 40dB. That's a 10,000 difference in level that are the result from how the SDS scanner operates and functions in relation to interference and overload issues. If you have the waterfall feature you can probably see more clearly whats' going on in the receiver.

A tower 30 miles away should not get you a -40dBm signal and a -80dBm reading seems more realistic.

/Ubbe

Come to think of it, I don't think I paused it when I was looking at the display so it may have switched to a different system.