Re: DVB-T signal meter
- From: Tony <Nospam@xxxxxxxxxx>
- Date: Fri, 13 Feb 2009 12:10:04 +0000
Bill Wright wrote:
"Alan Pemberton" <Spambox@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:1iu07eg.qy6zz6mgwqs0N%Spambox@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxBill Wright <insertmybusinessname@xxxxxxx> wrote:
I now have one of these meters on my desk. I'll report back shortly.
Well, it works. I have the SLX one. It does what it says on the can, but there is a snag, of which more later. Sensitivity is adequate to detect a Tx with five analogues and 6 digis at a level where the muxes are just useable. Possible if used where there are no analogue signals 20dB above the digis the sensitivity might be less impressive, but I didn't try it.
The four LEDs show only coarse level changes (10dB in fact, and quite consistent), so the advice is to position the aerial at the midpoint of the arc where most LEDs are on. A better way is to use a variable attenuator and carry out final alignment with it in circuit. This way the max signal is found accurately. An attenuator is also essential in strong signal areas. Here, 17 miles from Emley and LOS, all four LEDS stay on across a wide arc, and three are on with the aerial at any alignment or orientation. I'd say these gadgets will be essential after ASO for camping.
But there is, as I said, a snag. The device will not power a masthead amp, not will it pass power to one from the 'receiver' socket or from the built-in battery. The instructions say '5VDC 40mA, external power 5-12V DC. Clearly this is wrong, on several counts. The device has a PP£ 9V internal battery. Application of power to the 'receiver' socket has no effect below 5.4V at which point the four LEDs come on. With 12V applied they glow very brightly indeed. Thus the device does not function with power applied to the 'receiver' socket. This incompatibility with mastheads would be a snag for camping or fringe area work.
(Tested with a log periodic).
If they work, I might invest in one to optimise the reception from myI see no problem there.
Blake's LP. Trouble is, I'd have to shin up the 12-foot pole to get to
the F connector.
How about testing some of the gold-plated coax leads that Argos sellYes I'll do that for you Alan. Send me half a dozen samples.
while you are at it, Bill?
Bill
I've had a mapin one for some time, powered by external battery feed in by receiver connection point (F connector). Although it uses a 9V battery, I don't know if a 5V aerial power would work. Again it doesn't pass on the power.
I don't have a proper meter to compare with, but it seems to work and useful for pointing. It can give silly reading when nothing is connected and you touch the 2 terminal shields and the wire stand at the back.
There is a 4 LED version for £15, and an analogue meter one with variable 12dB attenuator for £20.
Sorry the link to the led on is broken, but here is the analogue one. I presume it is powered too by 9V in via F lead.
http://www.maplin.co.uk/Module.aspx?ModuleNo=227864
BTW we found the best way to check patch leads was a STB sensitivity on fall over, but really need to check at the higher frequencies and reference against a known good cable, although you really need a sig gen. The main difference was the plug shielding, the ones that are soldered on and just have the braid bunched and solder to the edge can lose 7dB at certain freqs, the better ones have a tapered clamped shield the pinches onto the braid on the cable. Unfortunately you can only tell this by cutting the moulding plastic off. The tapered shield is about 4 cents more per cable in volume, costing around $0.30 each.
--
Tony
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