Analogue to Digital MMDS issues

[Fano]

A friend of mine on Ch*rus MMDS recently bought a 500T.
He has an existing analog mmds setup.Its about 12 years old.
His analogue signal is excellent as he is very near the transmitter ~1 mile and has clear line of sight.
I connected up the 500T and all the channels came in at 99% snr but the ber starts off at 0 then jumps up and down and the picture keeps on breaking up.
I measured the signal strength on a meter and its very strong.
I thought initially it might be too strong so I tried a variable 20db attenuator but that made no difference.
I checked all the cabling and connections ,they are fine.
The analogue signal is perfect but the digital is unwatchable.
I tried a Digivox-T ,the signal was ~70% on it but it would drop alot.
Its odd that the analogue signal is so good and I cant more than a poor digital signal.
I had a look at his aerial ,its the Lance 24db type and the downconverter looks like it supports digital , (it doesnt have the white box on the back of the aerial like some of the older ones do )
The reception is generally better during the day but degrades at night.
I'm pretty stumped at this stage ,anyone have any ideas what it may be ?
Thanks

[tmontana]

exact same thing happend to my 500T fano, do a search, i made a thread about it, the tuner is knackered

[Fano]

exact same thing happend to my 500T fano, do a search, i made a thread about it, the tuner is knackered

Its a new box,the tuner is fine ,I tested it on another aerial.
Digivox-T box has the same issues,picture breaks up ,getting spikes in ber.

[despdan]

try a different power supply to aerial had same issue.
use the one from the other aerial

[tmontana]

have a brand new power supply fano, its yours if you want it, let me know

monty

[Fano]

try a different power supply to aerial had same issue.
use the one from the other aerial

Would that really make a difference ?
The one he used for analogue was 22v but it didnt have the necessary power inserter so I used an 18v Panorama one instead.
I could wire the 22v supply up to the inserter ,see if it improves things.
The analogue signal is fine so the aerial is being powered correctly ,would an xtra 4v be pivotal ?

[despdan]

I had same problem if you connect the power you used to test the box i bet it works. I tried 4 different power supplies before i got it to work. Was told after digital likes a nice clean power supply.

[Fano]

I had same problem if you connect the power you used to test the box i bet it works. I tried 4 different power supplies before i got it to work. Was told after digital likes a nice clean power supply.

I used the same power supply to test it I'm pretty sure.
It could be noisy though as I've had it along time.
I will rewire the 22v psu up ,worth a shot anyway,hopefully it will solve the issue.
Otherwise I will have to replace the downconverter,big job that.

[despdan]

pics

take a look at these the small one (bad)will power the downconverter but will only get analog . Big one will get digital perfect plus there is a 220v power supply on the back. The good one is about e25 zintec dublin. If your in the Mountmellick area i could let you test mine first.

[Fano]

Thanks for that advice Despdan.
I have used a few of the lightweight Panorama power inserters with different types of aerials and they always worked fine for Digital MMDS.

They are a bit flimsy but they do the job.
Sometimes the power unit can blow but I've rewired these with laptop psu's and similar.
The yagis will actually run off a 12v supply.
The big ones look very solid ,wouldnt mind getting one of them.
I'll rewire the old 22v Jerrold psu ,that will hopefully do the trick as 18v might be on the threshold of powering the downconverter although the spec for the required supply voltage are +15 to +24v.
The power inserter itself is quite a basic circuit.
You could make one at home.A suitable unit can be home made with nothing more than a scrap of PCB, a sharp knife, some 1 nF (1000 pF) capacitors, and a VHF RF choke (approx. 1 ?H)

[despdan]

I think my power supply is 18v but cant check till the morn.

[Fano]

I think my power supply is 18v but cant check till the morn.

Is the one you have a Friwo ,it looks like it,they are 18v allright.

[despdan]

Is the one you have a Friwo ,it looks like it,they are 18v allright.

Yes bang on mate 18v 350ma also have cal-amp downconverter yagi 16-24v see pic. You can test the downconverter connect the tv out straight to the tv & scan you should see the scrambled analog pictures & one clear channel sky news. Also when using the box disconnect the mmds feed for about 1 min goto signal finder set to 250000 & plugin the mmds feed in i have seen it lock for 1/2 sec then it stops.

[Fano]

Yes bang on mate 18v 350ma also have cal-amp downconverter yagi 16-24v see pic. You can test the downconverter connect the tv out straight to the tv & scan you should see the scrambled analog pictures & one clear channel sky news. Also when using the box disconnect the mmds feed for about 1 min goto signal finder set to 250000 & plugin the mmds feed in i have seen it lock for 1/2 sec then it stops.

Thanks for that info ,appreciate it.
The Cal Amp equipment is top notch.
With the bad power supplies were you getting any analogue signal when connected directly to tv ?
I get a perfect analogue signal with the current setup.See about 5 unscrambled channels.
I even put a 20db attenuation block on the analogue feed and its still a very good picture.
I must check if it is losing the sync and then try the 22v psu .
The downconverter is ~13 years old so its likely it might be too noisy for Qam64 and a digital signal.

[despdan]

Yes could get analog even with the aerial pointing off target. Sounds like there is nothing wrong with the downconverter you have but like you say i could be making noise. So its get a new power supply or get the ladders out i know which one i go for.