Multicoupler and Discone Antenna Setup

[VA3ADP]

Hello everyone,

I recently moved and now have new antenna setup. I went ahead and purchased a Stridesberg Muticoupler to pull in some more distant VHF/UHF systems as well. I am now using a DRA-220 I bought from Amazon a couple of years ago. I was originally using a Diamond mini discone at my old house and it worked great even with a shorter element, which made it great for indoor use.

Everything on most bands has been working well so far! However, I have had quite an issue receiving VHF systems and frequencies with this new setup (even the weather channels are barely coming in).

So my question is... is it the multicoupler or the antenna? Should I look at switching back to my old Diamond Discone or upgrade from my current one?

 

[Ubbe]

It's the antenna, or the scanners reception that are compromised from interference and for a SDS model you might have to use its different filter settings and IFX. The discone part are designed for something like 700MHz and above and will do well in that frequency band but it has a vertical dual band 144/430MHz tuned element and are very narrow banded. So not so well suited to receive the whole VHF/UHF range but probably better than the antenna on the scanner due to the elements sheer size.

/Ubbe

 

[cg]

Pretty quick check for the multicoupler would be to simply put a scanner directly on the antenna coax instead of the multicoupler. Go to your known weak channels and note any difference.

 

[VA3ADP]

I will take a look later tonight and report back. Also, should I be connecting my pre amp also? I am assuming there is a preamp inside the Multicoupler?

 

[Ubbe]

purchased a Stridesberg Muticoupler to pull in some more distant VHF/UHF systems as well.

It's designed to not attenuate a signal when you split it up to several scanners, so it will not improve performance, not much anyhow, for one single scanner.

Should I look at switching back to my old Diamond Discone or upgrade from my current one?

If all systems that you monitor, that are using 700MHz and higher frequencies, have a high signal level then switch back to the Diamond discone as it will have some 10-15dB attenuation in that frequency band compared to the DR220. Ideally you should have a diplexer that split up the signal from your scanners to one output for up to 500MHz and another output to handle signals above 700MHz and use both discones.

If diplexers are hard to find then use a low pass and a high pass filter, those can be had from MiniCircuits. If you take off the vertical element from the DR220 you probably only need a lowpass filter to the Diamond discone and at a frequency between 500-700MHz. Then preferable use a CATV 1-2 splitter that will have some 20dB isolation between antennas to its single output to a scanner.

/Ubbe

 

[dlwtrunked]

It's designed to not attenuate a signal when you split it up to several scanners, so it will not improve performance, not much anyhow, for one single scanner.
...

/Ubbe

There are actually two Stridsburg models with one (passive) attenuating (-4 dB and the other does have a pre-amp and gives between -1 dB (loss) and 2 dB gain depending on the frequency, and as you noted anything within that range cannot not be distinguished by a listener. Numbers above are their specs for the 2-port models. I did not see if he bought the active or passive one.

 

[VA3ADP]

There are actually two Stridsburg models with one (passive) attenuating (-4 dB and the other does have a pre-amp and gives between -1 dB (loss) and 2 dB gain depending on the frequency, and as you noted anything within that range cannot not be distinguished by a listener. Numbers above are their specs for the 2-port models. I did not see if he bought the active or passive one.

I purchased the MCM204A. I assumed the 12v power supply that came with it was to power the preamp inside of it? I was able to dig up my Moonraker Preamp this evening. I'll have to hook it up to the discone and then the multicoupler.

 

[Ubbe]

I was able to dig up my Moonraker Preamp this evening. I'll have to hook it up to the discone and then the multicoupler.

If you have the Moonraker version that has a gain controller, then set it to 0dB and listen to an analog weak transmission for the background noise or a digital signal that has some d-error values. Then increase gain until noise are lowest or digital errors are as low as possible. At some point values will go worse when you increase gain so you will have to back down to a lower gain setting.

If you instead have the fixed gain Moonraker amplifier you'll need to add a variable attenuator of your own and do the same procedure again or you will overload both the Stridsberg and scanner.

/Ubbe

 

[cg]

The active Stridesberg multicouplers only amplify the incoming signal enough to overcome splitting it. You essentially would have 2, 4, 8, or 16 ports (depending on the model) that had the same signal as the antenna.
The ones I have are MCA204 (4 port) and MCA208 (8 port) but perhaps those are old model numbers.