Masthead Pre-amp

[marcdeklerk]

Good day all,
I was wondering  how the A12-1090 Elad mast head pre-amplifier compare to the Kuhne KU LNA 1090 A TM Amplifier ?

 Do I also need a Bias T to supply the power the KU LNA 1090 A TM Amplifier ?
 -BT-12 Elad Bias Tee allows you to feed 12V to the  A12-1090

wil this one work? - Bias-T MKU 271 N
 
 
these products can be found at : http://www.wsplc.com/acatalog/RadarBox-2009.html#a8960

and

http://www.kuhne-electronic.de/en


KU LNA 1090 A TM Amplifier mounted into a water resistant case, NF typ. 0.5 dB, Gain > 30 dB 163,00 €


which above unit has the greater gain? DBi or DB?

thanks and looking forward to advise

Marc

[Mark07]

Hello Marc,
I cannot answer your technical query and I'm sure some of the knowledgable guys will.  I just want to say that I run the ELAD mast head pre-amp powered by the ELAD Bias-T (BT-12) and it works great for me.

If I disconnect the power supply I notice a decrease in my flights and the information being picked up.

I would recommend the set up.

Thanks,
Mark

[Deadcalm]

I had a problem with the ELAD, and it was replaced.  In the meantime I bought the Kuhne, and that has been running perfectly for nearly a year - I think it is of better construction generally.

DC

[jannuh]

When you disconnect the power supply you have an attenuator  ;)

[pjm]

When you disconnect the power supply you have an attenuator  ;)

Apparently there is a relay which bypasses the amp when the power is removed.

I received a faulty pre-amp with my antenna and when I apply power the pre-amp becomes an attenuator. Removing power and the Antenna alone works perfectly.

[CoastGuardJon]

Hi Marc, I'm far from expert, but the higher the DB figure, the higher the gain - DBI is a gain figure over an Isotropic antenna, as far as I know that is an omni-directional ("theoretically" perfect) antenna, with no nulls.

Pre-amps require a power source, which is usually 12v DC, directly connected by a psu in the case of the JIM M-75, or with external devices, such as the Elad or Kuhne which are mast-head amps, which get their power supplied through a Bias-T unit.   A Bias-T box has a connector from antenna, output to the scanner, RB, SBS or whatever, and a socket for the 12v supply to be input, the 12v does not go to the output side at all, but is "pushed" up the feed from the antenna where it is received by the pre-amp.    All extra connections incl. pre-amps and bias-Ts create some losses, and will also create some "noise of their own.    Pre-amps come into their own, if used at the antenna, to overcome the losses incurred by longer lengths of co-ax.   Also, bear in mind, if you've got a crap signal in the first place, a pre-amp isn't the cure-all some think, get the antenna and downlead sorted, would be my advice in the first instance, otherwise the pre-amp may just make the "noise" louder.

I hope this is of some assistance!

[landyman]

which above unit has the greater gain? DBi or DB?

thanks and looking forward to advise

Marc the decibel (dB) is a measurement of ratio.  It has no units and is a logarithmic scale.  But there has to be a 'zero' to measure against.

This is called an isotropic antenna.  It is a theoretical point antenna.  If is was possible to exist it would look like a very small pea.

If an antenna has gain it could be compared to this theoretical antenna.  If it's output voltage on receive was twice that of the pea, then it could be said to show a gain of 3 decibels.

But a practical term is required, so a dipole antenna is used as 'zero'.  So an antenna with twice the voltage of a dipole would have a gain of 3 decibels.  This is written as 3dB.

If the comparison was made against the pea it would be written as 3dBi.

As the the theoretical difference between a pea and a dipole is 2.1 dB this makes for confusion.

So an antenna advertised as 30dB would have the same gain as an antenna advertised as 32.1 dBi.

Does this help Marc?

Reg

[marcdeklerk]

Thanks very much!

[MW0CVW]

Hello All,

My comments on the Elad 1090mhz Lna with the bias tree as follows.

1.Poor electronic and mechanicial construction.

2.Major U.K equipment supplier admits,this product is not very reliable

I returned my unit and a a full refund.

The KU LNA 1090 A TM Amplifier mounted into a water resistant case,no relays less (signal loss) and better construction and good technicial support.


Would be even better if there was a supplier in the U.K.

Paul

MW0CVW

near EGNR/EGGP

[CoastGuardJon]

Hi Paul, thank you for that, I'd heard the same re. Elad from another source, so would assume your assertions about the Kuhne (Rolls Royce) are spot on.

[MW0CVW]

John,

The Kuhne LNA is the Rolls Royce and would be my choice.

Not much cost difference (Elad) but a better product by far.

My profession for 25 years was in RF communications,so no quality and performace when i see it.

Hope this helps.

Regards

Paul MW0CVW.

[landyman]

The KU LNA 1090 A TM Amplifier mounted into a water resistant case,no relays less (signal loss) and better construction and good technicial support.

Would be even better if there was a supplier in the U.K.

Looking on his ham pages
http://www.kuhne-electronic.de/db6nt/english/db6nt.htm
one can see the quality of Michael's work.

But the 1090 is not in the price list.

As for the lack of a UK supplier, that should be no problem.  I remember buying a German ATV transmitter kit in about 1971, when a pound sterling got over DM 9,0 and it arrived quickly.

These days with a credit card purchase (preferably Nationwide as their charges are much less) items arrive from Germany often faster that a UK supplier, in my experience.

Ironically, earlier today I was considering the opposite of a head amp.  I monitor military aircraft and have alerts setup, so that I can be outside with my camera.

I can receive aircraft in/out of BZN which is over 200km from here, but no chance of seeing them.  So I'm thinking of making a 3 element beam, pointing the other way or shielding the standard antenna that's on the window ledge.

Possibly a small 2 or 3 element beam pointing in the area of interest could provide a cheaper solution than a head amp.

Reg

[CoastGuardJon]

Hi Reg, there is a price list on his web-site  KU LNA 1090 A TM (the exterior mast-head version in waterproof case) is €163.00 and the Bias-T KU BT 271N is €47.00.

It sounds as though you'd be better off with a colinear or dipole on a rotator, but that ain't going to fit on the window ledge!   Have you thought about trying sticking a lemonade bottle over the standard antenna with length of self-adhesive aluminium tape down the side as a screen - if you haven't got any tape, PM me and I'll stick 30cm in the post.    I used some many years ago on a Shakespeare homebase antenna - can't remember which model, but the whip was about 8' long and the lower section about 9½' long, the copper screen in the lower section for ground was pathetic, about 8 strands, which I removed and replaced with the aluminium tape wound spirally down the inner former - you can actually solder to the aluminium tape.   I also built a replacement inductor trap, and turned a reasonably good antenna into a superb one.

[landyman]

Thanks for your reply.  I must be going blind !!  I searched up and down umpteen times and never saw it, embedded in the ham amps.  But in correct frequency order.

I like the suggestion of the bottle and aluminium tape.  I just put the antenna on the window sill as I got it out of the box, intending to put it higher outside after weatherproofing it.  But it works very well in that position.

Thanks for the offer on the tape, but I have some.

Reg

[jaskel]

so would a digital tv masthead amp work? 32db gain unit with f type connectors, i know the freq only goes to 860mhz but should still boost the signal?