BCD536HP and SDS200

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shirsch101

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I just bought a BCD536HP a few weeks ago and I am thinking of exchanging it for a SDS200. The BCD does not really handle the Simulcast in my area all that well and from what I see on these forums is the SDS200 is the way to go...any comments?
 

jonwienke

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Maybe a better question is how does the SDS compare to a 536 in a certain band with/without strong adjacent signals?
The SDS models are somewhat more susceptible to interference from strong adjacent signals than the x36 modelos, although most of the time that can be dealt with using filters and/or IFX. But that has nothing to do with digital/analog.
 

Ubbe

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The SDS scanners have a pre-amp built into it that makes them more sensitive. When connected to a signal generator the SDS have better sensitivity in all bands. When connected to an antenna the SDS have a higher risk of getting interferencies and it is the same in all bands. I have very low RF signals in the low-VHF and VHF air with hardly anything that can interfere. There the SDS have the best sensitivity compared to a 536. In UHF I have a lot of low level signals with almost the whole spectra fully occupied with transmitters. There the SDS are difficult to use as it looses sensitivity and gets interfered very easily and no filter settings or IFX helps, it just moves the interferencies to other frequencies where they create problems to other monitored frequencies. My signal levels are -80dBm or lower so it shouldn't be a problem but the SDS behaves similar, if not exactly, as my $20 SDR dongles.

/Ubbe
 

twotoejoe

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I've got both the 536 and 200. I don't monitor simulcast so can't comment on that. The best difference that I can tell it the display on the 200. You can read the 200 so much better!

I've been having a problem with the 200 not picking up all the signals that the 536 does. I've set them side by side, exact same programming thru Sentinel, both on the original telescopic antennas. The 200 is chopping off the first of the transmission, dropping the reply, or missing the transmission altogether. I hope this is just unique problem for my radio only.
 

bberns22

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I live near you and monitor Chester County. As I replied to you, in another thread, the 536 is not optimal for Chester County's Harris System. Not only is simulcast an issue but Harris Systems seem to be configured in a way that makes audio intelligibility more difficult than other P25 systems. I don't know why but bet someone here can explain the technical reasons.

I suggest you purchase an SDS unit or Unication G4 or G5. My Unication is superior to my SDS 100 & 200 for the Chester County system as it manages simulcast better and produces clearer audio. The downside is the lack of scanner function flexibility.

The SDS units do a very good job with Chester (90% as good as the G5?) and offer far more flexibility. As for UHF , using the same antenna, the SDS's are just as good as my Realistic Pro-2021, Realistic Pro-2005, Realistic Pro-2006, and number of other analog receivers I have on hand. Using a paper clip I can receive receive DE county sectors 1&3 no problem...

You will not need that discone for Chester County or DE county and, in fact, it will make Chester simulcast worse given the location of the transmitter sites relative to you. A good 800mhz rubber duck is all that is required to hear Chester and DE CTY systems. I am not sure what other systems you want to hear but the 2 closest, Montgomery & Lancaster counties, are 100% encrypted. I guess you might be able to hear Wilmington DE sites but the rest of DE is also 100% encrypted. So you can ignore the comments on interference and IF issues. At our location 90% of all transmissions are 700mhz/800mhz P25 and coming from a single system. DE county's closest UHF site is almost 5 miles away; we do not live in a high RF environment.
 
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Ubbe

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You can listen to the audio file how it sounds when a moderate level 800Mhz signal are applied from a signal generator and how it affects most other frequencies in the band. Do your own monitoring from your antenna in analog mode in the 800Mhz band.

Actual test of a SDS100

/Ubbe
 

bberns22

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You can listen to the audio file how it sounds when a moderate level 800Mhz signal are applied from a signal generator . and how it affects most other frequencies in the band. Do your own monitoring from your antenna in analog mode in the 800Mhz band.

Actual test of a SDS100

/Ubbe
I reviewed the link you provided and I don’t think it is relevant to this discussion. At his location neither of the two systems will desensitize, cause intermod or IF related issues. As I stated we do not live in a high rf environment like New York City or Chicago. And frankly, I have not heard of this being an issue from others SDS users on 700mhz/800mhz P25 systems. Maybe UHF Reception in a New York City highrise might suffer from what you describe but the Chester County system is 30+ years, ahead and 1000x more efficient than those ancient analog uhf systems. But I will admit I prefer analog uhf from a reception and intelligibility perspective - big power and loud audio make for good listening....
 

AB5ID

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This is probably a dumb question but is it possible for a SDS scanner to be desensitized by one 800Mhz P25 trunked system with adjacent voice channels transmitting simultaneously or is frequency spacing large enough to not be a factor?
 

Ubbe

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The automatic reduction of gain to help the receiver from getting overloaded are sensing RF levels from a wide spectrum. But if you monitor signals of equal strenght, like one system site from one tower, they will all have the same strenght and the SDS scanner adapt to that signal level, so no problem that one of the frequencies will be too low in level and not heard or decoded properly.

It will only be a problem if another much stronger transmitter using a frequency within the working range of the RF sensor will make the scanner reduce its gain where a weak signal are not heard anymore. But what handicaps SDS scanners are interferencies that create data decode errors and distorsion in analog transmission. In the example with a single -60dBm signal there are more than 50% of the frequencies that are interfered. In real life you will have many more signals in the air at the same time and the problem will occure at lower signal levels and be much more severe.

/Ubbe
 

jonwienke

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In theory.

In practice it's an issue far less often than you claim.
 

bberns22

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In theory.

In practice it's an issue far less often than you claim.
Exactly the point I was trying to make, especially where the OP lives (and myself). I have had the SDS units in Manhattan (probably a worst case as it pertains to uhf rf overdose in the USA) and I never experienced any of those symptoms.

Back to the thread. The SDS units work well and as you live in Chester County they are the only option if you want full scanner functionality and reliable reception of our Emergency Services System. If you can live with the limitations of a G4 or G5 then you will be rewarded with even better receiver performance.
 

bberns22

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One other thought - I found adding something like this for dedicated VHF / UHF, on top of your digital radio, in our area is useful for monitoring DE County and the 3 VHF re-broadcast fire frequencies in Chester. Older radios like these are abundant and cheap. During this pandemic I acquired 4 or 5 and have refurbished them - really nice...
 

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shirsch101

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So instead of spending the extra money and trading up to the SDS200 I thought I would switch to the outdoor discone antennae I have mounted outside and the simulcast channels in Chester County has great improved to where it is listenable now. May be at a later date I will get the SDS200 but for now the BCD536HP is working good for me
 
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