Multiswitch faulty?
Ron Lowe
I have a strong suspicion that my Antiference iSys-7 x 12 multiswitch
has just failed. It looks like it has stopped passing UHF!
I was just setting up a TV in the guest bedroom, and noticed the analog
channels were very snowy and weak, particularly CH5 ( uhf 67 ). Other
analog channels ( grp A ) weak but watchable.
Digital channels seemed fine, but signal strength was showing lower that
I expected.
After some investigation, it seems that the multiswitch is simply not
passing ANY UHF, to any of it's outputs. If I bypass the multiswitch,
and feed the outlet's downlead directly from the switch's 'UHF in'
cable, all is good.
Patching back through the switch, all is bad.
If I simply unplug the downlead from the switch and leave it hanging in
free air, then I get around the same signal as through the switch!
Seems the only UHF I'm getting is residual pickup in the downleads!
It seems to me that digital is only working because the recievers have
enough sensitivity to pick up residual signal being picked up by the
downleads! ( I'm close to a main Tx. )
Does it seem likely that the switch has simply gone belly-up?
Any recommendations for a replacement?
The Antiference seemed fine whilst it was alive.
My brother installed a triax TMP 5 x 24 and it seems to work OK, but I'd
need to combine the UHF / FM /DAB externally.
--
Ron
-<GB>-Carpy
"Ron Lowe" <d...@null.com> wrote in message
news:haaspc$oa$1...@news.eternal-september.org...
These switches have a feature where they cut off all the UHF / VHF side if
there's a problem with the DC power. I killed one by connecting a log
periodic to the UHF input and not putting the supplied DC block on first.
Presumably you've done the same!
Ron Lowe
No, I have the capacitive DC-blocker installed, following a similar
experience at install-time.
( Incidentally, the DC-block is not mentioned once in the documentation
supplied with mine. I just figured it out from first principles. )
The Taylor channel filters / levelers on the UHF input upstream of the
switch presented a DC short to the multi-switch, and the red LED for
head-amp power went out, and the PSU section became hot. After
figuring out the problem, I installed the DC blocker and the red light
came back on and normal service was resumed.
It is possible that this little escapade did actually damage the switch,
though. It may have precipitated a later failure.
The red head-amp power light beside the UHF input remains on, indicating
the PSU is happy, but other gubbins may not be.
--
Ron
Stephen
and the multiswitch?
I have 3 aerials, one is FM, one is DAB, one is UHF and they go to a
amplifer that has three inputs and has a gain control for each input in the
range of 0 to 20dB.
This then provides a combined amplified single output that then goes to my
Triax 5x16 multiswitch.
As I understand it, Multiswitches don't amplify the UHF/VHF, so when you're
splitting 16 ways as in my case, you need to have quite a high input UHF/VHF
signal to the multiswitch to deal with the inevitable reduction in UHF/VHF
signal strength due to the passive splitting within the unit.
Regards
"-<GB>-Carpy" <ca...@nothanks.com> wrote in message
news:vW7ym.1117$UJ3...@newsfe13.ams2...
Bill Wright
"Stephen" <i.wan...@spam.com> wrote in message
news:i_idnUIOB5FcjVTX...@brightview.co.uk...
> Aren't you supposed to use an UHF/VHF amplifier between the UHF/VHF
> aerials and the multiswitch?
need to be attenuated.
> As I understand it, Multiswitches don't amplify the UHF/VHF, so when
> you're splitting 16 ways as in my case, you need to have quite a high
> input UHF/VHF signal to the multiswitch to deal with the inevitable
> reduction in UHF/VHF signal strength due to the passive splitting within
> the unit.
The only switches that don't amplify the V/UHF are the ones that don't have
a power supply, instead relying on receiver power. These will typically lose
17dB for an 8 way switch. Such switches are a rarety. The powered ones
always use amplification and generally have gain to each output of
between -3dB and -8dB.
Bill
Bill Wright
"Bill Wright" <insertmybu...@f2s.com> wrote in message
news:hYqdnUIlI9P_ulTX...@pipex.net...
Typo: that should have read 'between -3dB and +8dB.'
Bill
Brian Gaff
Brian
--
Brian Gaff - bri...@blueyonder.co.uk
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"-<GB>-Carpy" <ca...@nothanks.com> wrote in message
news:vW7ym.1117$UJ3...@newsfe13.ams2...
>
-<GB>-Carpy
Sounds like you've semi-killed it ! Same thing happened to me. It appeared
to have damaged the power supply to a certain degree, but mine failed
completely a short while later.
Ron Lowe
>>> These switches have a feature where they cut off all the UHF / VHF
>>> side if there's a problem with the DC power. I killed one by
>>> connecting a log periodic to the UHF input and not putting the
>>> supplied DC block on first. Presumably you've done the same!
>>
>> No, I have the capacitive DC-blocker installed, following a similar
>> experience at install-time.
>>
>> The Taylor channel filters / levelers on the UHF input upstream of the
>> switch presented a DC short to the multi-switch, and the red LED for
>> head-amp power went out, and the PSU section became hot. After
>> figuring out the problem, I installed the DC blocker and the red light
>> came back on and normal service was resumed.
>>
>> It is possible that this little escapade did actually damage the
>> switch, though. It may have precipitated a later failure.
>>
>> The red head-amp power light beside the UHF input remains on,
>> indicating the PSU is happy, but other gubbins may not be.
>>
>> --
>> Ron
>
> Sounds like you've semi-killed it ! Same thing happened to me. It
> appeared to have damaged the power supply to a certain degree, but mine
> failed completely a short while later.
Yes, I think so too.
In retrospect, I'm no longer sure it ever worked properly after the
incident. I think I may have been watching digital on residual signal
all this time!
So do I replace like-for-like, or go for something different...
--
Ron
Ron Lowe
> So how does that blow the system up then?
> Brian
>
The switch provides 12v DC power up the UHF inlet, to power a masthead
amp if required.
There's apparently no protection on this, and if the aerial / filters
whatever upstream from the switch presents a DC short circuit, it shorts
the 12v often catastrophically. The PSU section runs very hot during
fault conditions.
Even after removing the short, and the 12v seems to recover, the
multiswitch may never pass UHF again :-(
Short of pulling it apart and screwing around, I can't say anymore.
But that appears to be the general way of it.
--
Ron
Bill Wright
I'm a bit puzzled by all this. We use Anti switches and I wasn't aware of
this problem. It's perfectly possible though that I've never used one with a
DC short on the UHF input. They are normally fed by a pre-amp followed by a
splitter of some sort.
I have noticed though that if the terr gain is at max there is a noise
problem (disturbance on analogue pics, slight BER degredation on DTT). Turn
the gain down 2dB and it's OK.
Bill
Stephen
If I connect my oxford aerial direct to a TV with a maxview MHA23US masthead
all is fine, muxes come in loud and clear. the same applies to the FM aerial
to a FM radio, and for the DAB aerial to a DAB radio.
Once I put the Triax multiswitch in, the satellite feeds from the quattro
LNB is fine, but the UHF, the FM and the DAB all fall over.
When I put in the Antiference three input amplifier in between the 3 aerials
and the mulitswitch, all was back to normal.
Regards
Stephen.
"Bill Wright" <insertmybu...@f2s.com> wrote in message
news:hYqdnUIlI9P_ulTX...@pipex.net...
>
-<GB>-Carpy
"Ron Lowe" <d...@null.com> wrote in message news:4ACA1933...@null.com...
Just get another one but use the DC block straight away! These amps (and the
terrestrial only ones) are great & I use them all the time, costly though
they are. I'm pretty dismayed with lots of Antiference products these days
but the amplifiers are really good.
I tried switching to Labgear once for cost reasons, and the failure rate was
about 20% which was just plain silly. To top it off, Labgear didn't want to
know about the problem with these amps so I've boycotted their products ever
since!
I've probably installed well over a thousand Antiference amplifiers by now,
and I can only recall 2 that I have had to go back and swap out. Pretty good
stats & for me well worth paying the extra for.
On a side note I tried a few of the Proception Solo Starboxes recently, and
really liked them. It's a shame that everywhere I go to / order from always
has the Proception stuff (normal amps included) as a "special order" item
meaniing I never order any. Tried the mastheads ages ago and they were
fantastic, albet a bit "beige" and dull looking.
Ron Lowe
> I have a Triax 5x16 multiswitch in my loft which is mains powered.
>
> If I connect my oxford aerial direct to a TV with a maxview MHA23US masthead
> all is fine, muxes come in loud and clear. the same applies to the FM aerial
> to a FM radio, and for the DAB aerial to a DAB radio.
>
> Once I put the Triax multiswitch in, the satellite feeds from the quattro
> LNB is fine, but the UHF, the FM and the DAB all fall over.
>
> When I put in the Antiference three input amplifier in between the 3 aerials
> and the mulitswitch, all was back to normal.
>
> Regards
>
> Stephen.
>
Doesn't sound right.
Is the input signal marginal to begin with?
If it's not, then the insertion loss ought to be minimal.
Sounds like yours is bu**ered too :-)
--
Ron
Ron Lowe
>> So do I replace like-for-like, or go for something different...
>>
>>
>
> Just get another one but use the DC block straight away! These amps (and
> the terrestrial only ones) are great & I use them all the time, costly
> though they are. I'm pretty dismayed with lots of Antiference products
> these days but the amplifiers are really good.
Thanks.
I'd pretty much decided to do this anyway.
Now to go a googling for a decent price.
OT:
SWMBO has decreed that I must investigate $ky for Xmas: junior has
become football mad, and we apparently need $sk. ( I think a DNA test is
in order. )
Anyways, on the subject of sky... when the sky installer arrived at my
brother's house some time back, with explicit instructions to simply
plug the box into the existing multiswitch distribution system, the guy
*insisted* that since it wasn't a sky dish, it wouldn't work. He had
convinced my brother's wife that he was going to install a mini-dish,
and drill a hole in the wall. My brother had to come home from work to
convince the installer of the error of his ways. In the discussion, it
became apparent that the 'installer' had no knowledge whatsoever of
multiswitches.
How is it possible to do sat installs and not know about multiswitches?
Every block of flats etc must have such a setup. It's just not
concievable that he could have no experience of such thing. Perhaps
they send their 1st day juniors out on 'domestic' 'bodgit quick' jobs?
--
Ron
Bill Wright
> -<GB>-Carpy wrote:
> Anyways, on the subject of sky... when the sky installer arrived at my
> brother's house some time back, with explicit instructions to simply plug
> the box into the existing multiswitch distribution system, the guy
> *insisted* that since it wasn't a sky dish, it wouldn't work. He had
> convinced my brother's wife that he was going to install a mini-dish, and
> drill a hole in the wall. My brother had to come home from work to
> convince the installer of the error of his ways. In the discussion, it
> became apparent that the 'installer' had no knowledge whatsoever of
> multiswitches.
>
> How is it possible to do sat installs and not know about multiswitches?
It's fairly normal. I had a customer 50 miles from here who rung up because
the Sky man (swapping a Sky+ for a Sky HD) insisted that the dish (a 65cm)
was 'one of the old types' and had to be replaced. Furthermore the only way
the three receivers could be made to work was to have two dishes. This was
despite the fact that the existing receivers were working fine. The 65cm
dish was feeding into a switch of course. In the end I had to travel down
there to meet the Sky 'engineer'.
Bill