Troubled Antenee for Basestation, help.

[John Roe]

Can some one advise me Please, I built the above Antenna 8 years ago, the past 2 years I have had several problems involving Base Station that Anmere has fixed for me, to his unbelief also to why the Antenna did not work and over the past 2 years , believing that was then the root cause of the Base Station failing each time it was re installed, anyway, having got it down from its 27m perch , I test it again to see the meter reader shows a short circuit, not seeing anything obvious broken, I consult the scumatics construction again to discover, forgotten about, the 1/4 wave at the end is bent around and soldiered on the outside, of course it will show a short, have, next then power booster ( Klune L-Band Super L:ow Noise Broadband Amplifier  KU LNA 1000 A-TM ) Tested or new. has 12 volts to it, up the coax, checked the coax cable , one length, no joins, the booster was sent back to Germany and tested, all ok, returned, bought a new anyway, not used yet, so when connected as Anmer tested, nothing, ive tested it heaps of times, same result, so what can then problem be, no visible cracks in soldier joints, continuity thru all joints,  cable joints clean, use to have a 270 NM radius signal, nothing now, old magnetic works well in the office upon pencil sharpener. short range, Base station still has a couple errors in it like the range line  looks anywhere,  nothing serious, any one can advise,  thankyou  cheers john

My memory flashes back to 2 yrs since this computer error started with Basestation, was it, or is it something to do with changing to a new unit , some thing to do with the antennae as well, need to get another computer to eliminate the aerial problem,,   john

[Anmer]

Hi John

What diameter coaxial cable do you have?  Sometimes a tight bend can cause hidden damage.

Have you tested your external antenna with different cable, even a short length?

[John Roe]

Hi Anmer,
No im not sure about the cable, I think from my old notes it is thick 1090 MH, 35 feet, sounds right to me, or could have been BS1105, but first sounds right because of length,
would be so difficult to connect antennea inside house to Radar Box, and no have not tried that, but do not have any other cable,  the run is one piece length, about 35m long,  if able to connect to box direct, like we did with magnetic, would you use the Power Booster as well,   did you see my last edit to main comment.  john

[Anmer]

Thanks John.

Your SBS works OK with the supplied magnetic, indoor antenna.  I have seen this working.

The issue you have is your external antenna setup, not your computer or SBS.

Finding the problem is the challenge, especially as you can't easily dismount the antenna and test with different cable or the cable with a different external antenna.  If you have a masthead preamp, this could also be a contributing factor.

[John Roe]

Thanks  Anmer, well next move is to re soldier the head back on the Colliner and see if it can be connected in here like we did with the magnetic, with or without the new Preamp. standby for the results in a couple of days,   john

[Truetrack]

There may be a remote chance
overload ?
Preamp cut out ?
a) with a possible loss of ~ 8 dB for any 7mm OD type cable at yr length/1GHz
   or about loss apprx ~ 5dB for any 10mm OD type at your length/1Ghz
understand the Kuhne gives 30 dB of amplification.
Many people assume the greater the better and their setup gets a long with it,
but in extreme situ it may overload the input of the receiver.
Thus even reducing reception.
b) you say 12VDC going up ? or is actually up there?
  If the supplied DC is as the Kuhne mentioned below +8 V a Preamp may cut out
  which may cause poorer reception than straight forward without an Preamp.

Wish you a good outcome to your troubleshooting

[John Roe]

Thanks Truetrack for that advice, I measured the power at the head of cable other day and set multi meter at 20v DC and read 8.47 volts, based on the meter set on 20v, I guessed that to be around 12 volts, last night I read the meter at the base, at same rating of 20v to read 12,76 volts, then my guess was that the transformer was under voltage now?,  I am yet to test the antenea inside with out the pre-amplifier. 

I was not one to assume and go bigger and better in the construction of the setup, that was done under the late supervision of an enthusiest Basestation user, the system worked for 4 yrs until an Basestation error occured, since then there has been an antenea issue, there is no seen fault with the antenea, hence an inside connection test will be tried along with a test with another transformer. the head test again, can not be performed without the hire of another 35m cherry picker, john,

30/3  A test with the antenea inside the house connected the radar box proved 0 results, next is as its a easter long weekend, on tuesday to have a 3m cable made and temp put the antenea on the roof to prove indifferent, any signals received with this troublesome antenea,  cheers

Footnote: short cable made from advice, antenea put on roof, signal good 151nm, re check power, not good, possible PSU, no, further check, power cable plug, 2 broken wires just touching in housing, uggg, 2 yrs to find,, thanks to all who helped with possibilitys of issue, now to get it back up mast to see 270nm ac again,  thankyou all john..

Wed 11th Apr,  Well devistation, tried antenea on roof with a short cable, good, 151nm received, take it back up mast, connect antenea and new Kuhne brand new amp , check stitu, down below, nothing, check voltage, nothing, get new power supply, 19.15 volts input at cable splitter, good, now, still nothing with tested antenea, new amp, new PSU with input confirmed at 19.15 volts, so WHY .. nothing, had my Electrical Engineer test and calculate input volts to be 19volts for 12v + at mast head, but at now we do not know unless I get cherry picker back at another $400 to read power out at top, then whats next,  will try lower input voltage.. losing patience with this.. grrrrr.. john.

[John Roe]

Wed 11th Apr,  Well devistation, tried antenea on roof with a short cable, good, 151nm received, take it back up mast, connect antenea and new Kuhne brand new amp , check stitu, down below, nothing, check voltage, nothing, get new power supply, 19.15 volts input at cable splitter, good, now, still nothing with tested antenea, new amp, new PSU with input confirmed at 19.15 volts, so WHY .. nothing, had my Electrical Engineer test and calculate input volts to be 19volts for 12v + at mast head, but at now we do not know unless I get cherry picker back at another $400 to read power out at top, then whats next,  will try lower input voltage.. losing patience with this.. grrrrr.. john.

[Anmer]

Hi John

What "cable splitter" and where?

[John Roe]

Hi Anmer,

Well thats what I call it, a very small metal box that the main thick cable passes through with a power  adapter where the voltage is inserted into, that the current runs one way up the cable almost imediately behind the  BS Box , I changed last night, the inn current from 19.45 volts to 16 volts, no difference. if the voltage was too high because of my electricians calculations, then the pre  amp may be cooked now, good bye another 400 bucks,,

[Anmer]

Sounds like a Bias-T where you "inject" the power for the masthead preamp?

If the antenna on the roof works with a shorter cable (I assume without the Bias-T?) then the longer cable may be shorting.  Not enough to show up on a continuity electrical circuit test but degrading the signal.

Try and eliminate possible issues, one by one.  Cable, connectors, Bias-T, power supply and preamp.

[John Roe]

Question to any one, do we have to have the Pre Amp at the top of the mast, 27M high, for a good  signal to be received.

Also been told to check the center pin in cable has not pulled out, have to loop wire to top or bottom to create continuity test.

[Anmer]

Placing an amplifier at the base of the antenna should only amplify the signal as received.  Putting it at the end of the cable run, nearer the receiver, will amplify the received signal and any induced noise from the antenna to the amp.  Well that's how I understand it.

As I suggested before, work your way through each component to find what causes the drop in signal strength.

I'm getting good coverage with antennae used without amplifiers.  Height is the main benefit. 

[John Roe]

Hi Anmer,

Better re phrase the question, can we do away with the pre amp altogether and get the same or simular results, my case up to 270nm..   john.

[Anmer]

I think the answer is "Yes".

What you might lose without the amp are weaker messages from aircraft within 270nm but maybe at lower altitudes.  Or you will track for less time.

If you dump the amp, dump all the bits associated with it, including the Bias-T.  That's why I suggested, where you can get at it, removing all the components one at a time to find the guilty party.