best antenna

[abcd567]

... sorry it's an equivalent ... HDF400, it's not too bad on the outside diameter maybe 9-10mm - but the inner conductor looks like something that could be used to build suspension bridges - same attenuation factors and impedance of as LMR400.

Not
sure if this will help but I use RG-11/U. I needed 75ft of it and there is very little loss at that length plus it is relatively inexpensive, although difficult to find someone to sell it to me. My aerial is the one from 1090MHz mounted on a pole on my chimney.

@1090 Mhz Attenuation of 75 feet:
RG6 = 6.1x75/100=4.5dB
RG11 = 5.6x75/100=4.2dB
LMR400=3.6x75/100=2.7dB

Advantage in using LMR400 instead of RG6=4.5 -2.7=+1.8dB

Advantage in using RG6+13dB Amplifier =13-4.5= +8.5dB


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[abcd567]

.......the inner conductor looks like something that could be used to build suspension bridges......

Such a conductor is good where power runs in hundreds or thousands of watts, an ideal cable for transmitters. For receivers power is in milli, rather micro watts, and a hair-thin wire may prove enough.


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[747-8F]

Do you this will work to connect receiver to coax cable RG6, i mean to transfer data?

http://www.ebay.com/itm/6inch-RF-coaxial-cable-F-female-to-MCX-male-right-angle-RG316-/271220031032

[Amper]

Do you this will work to connect receiver to coax cable RG6, i mean to transfer data?
http://www.ebay.com/itm/6inch-RF-coa...-/271220031032

i use it, works perfectly

[abcd567]

Do you this will work to connect receiver to coax cable RG6, i mean to transfer data?
http://www.ebay.com/itm/6inch-RF-coa...-/271220031032

I have cut the wire from the stock antenna which was supplied with the DVB-T Dongle, and soldered the wire to a solderable F-connector available with me, and It became the same thing you have shown. It works perfectly well.

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[747-8F]

i use it, works perfectly

I have cut the wire from the stock antenna which was supplied with the DVB-T Dongle, and soldered the wire to a solderable F-connector available with me, and It became the same thing you have shown. It works perfectly well.

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Excellent thanks alot I will order this right away

[abcd567]

Remember when satellite tv newly arrived?
Dishes used to be 3 meters in dia. Now 0.5 m dia.
Why? More power pumped by sarellites up in sky+much more powerful pre-amp in LNB.

Remember when cell phones newly arrived?
Antenna poking out. Now antenna so small, it does not poke out.
Why? More powerful cell phone pre-amplifier.

Conclusion: use "moderate gain antenna+moderate quality cable+amplifier".

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[1090 MHz]

Remember when satellite tv newly arrived? Dishes used to be 3 meters in dia. Now 0.5 m dia. Why? More power pumped by sarellites up in sky+much more powerful pre-amp in LNB.

The Big Ugly Dishes from the 1980's "BUD's" in those days they used C band @ 4GHz. Even today you'll need a BUD to receive C band... some people still do use those BUD's

In the early 1990's RCA and Hughes Aerospace teamed up to develop the Direct to Home TV system. The system utilized a much smaller and more practical earth station antenna. This was accomplished by using a much higher frequency, ku Band @ 12 GHz. Also more gain was accomplished by using circular polarization... unlike linear polarization ... circular polarization is a spinning signal wave that paints the entire dish surface, making the smaller antenna more efficient... also they went with an off-set feed (LNB) so that no feed horn support arms were blocking any of the signal like they do on BUD's.

The LNB's do also have a much higher gain, but also a much lower noise temperature. Newer satellites do run at a higher power, but this is more to overcome rain-fade issues that are a common problem with Ku band, and the main reason cable and network broadcasters still stick with C band as it's more reliable in bad weather.

[abcd567]

The Big Ugly Dishes from the 1980's "BUD's" in those days they used C band @ 4GHz. Even today you'll need a BUD to receive C band... some people still do use those BUD's

In the early 1990's RCA and Hughes Aerospace teamed up to develop the Direct to Home TV system. The system utilized a much smaller and more practical earth station antenna. This was accomplished by using a much higher frequency, ku Band @ 12 GHz. Also more gain was accomplished by using circular polarization... unlike linear polarization ... circular polarization is a spinning signal wave that paints the entire dish surface, making the smaller antenna more efficient... also they went with an off-set feed (LNB) so that no feed horn support arms were blocking any of the signal like they do on BUD's.

The LNB's do also have a much higher gain, but also a much lower noise temperature. Newer satellites do run at a higher power, but this is more to overcome rain-fade issues that are a common problem with Ku band, and the main reason cable and network broadcasters still stick with C band as it's more reliable in bad weather.

Thanks a lot for providing very useful & enlightening information.

[abcd567]

See the DIY DC Power Inserter shown in the image below.
Found it on web today, but did not try it yet.
Looks interesting.
DC-Inserter.jpg

[mickopla]

Best termination is centre core with white insulation poking out 66mm as a 1/4 wave whip at the top of the coco. (outer sheath & braid stripped ... I think thats what your 5.5cm section is but it takes into consideration the velocity factor - which is not needed if it's just a whip antenna.

Just to clarify my last section needs to be 11cm long of which 6.6cm will be the whip? I'm still waiting on my dongle to arrive so can't test anything yet. I ordered via Amazon.co.uk over two weeks ago now and its seems its been shipped from the US. Frustrating having to wait so long.

Mike

[peterhr]

See the DIY DC Power Inserter shown in the image below.
Found it on web today, but did not try it yet.
Looks interesting.
[ATTACH=CONFIG]3018[/ATTACH]

This would mean the sheath is running at -15v or something, rather than running the core at +15v ... should something get grounded on the mast and the reciever end - there is more possibility of getting +15v appearing at the RF input of the receiver. Now the question comes down to does the receiver have a voltage blocking capacitor on it's input.

I think I'll give it a miss.

Just to clarify my last section needs to be 11cm long of which 6.6cm will be the whip? I'm still waiting on my dongle to arrive so can't test anything yet. I ordered via Amazon.co.uk over two weeks ago now and its seems its been shipped from the US. Frustrating having to wait so long.

Mike

.85 * 13.2 = 11.2cm with outer sheath + braid,
then 6.6cm bare or with insulator only

11.2 + 6.6 = 18.82 cm

Assuming .85 is your cable velocity factor

[abcd567]

This would mean the sheath is running at -15v or something, rather than running the core at +15v ... should something get grounded on the mast and the reciever end - there is more possibility of getting +15v appearing at the RF input of the receiver. Now the question comes down to does the receiver have a voltage blocking capacitor on it's input.
I think I'll give it a miss.

Your logiic seems right. The shield is grounded at receiver. Even though DC circuit is broken by breaking the sheild, an alternate DC path through earth is ceated if amplifier body or the shield at antenna is grounded, either inrentionally or unintentionally.

Breaking DC by breaking central conductor is much safer than by breaking the shield.

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[peterhr]

Your logiic seems right. The shield is grounded at receiver. Even though DC circuit is broken by breaking the sheild, an alternate DC path through earth is ceated if amplifier body or the shield at antenna is grounded, either inrentionally or unintentionally.

Breaking DC by breaking central conductor is much safer than by breaking the shield.

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Also needs a choke on the positive so the power supplu doesn't provide a short circuit to the signal.

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[abcd567]

Also needs a choke on the positive so the power supplu doesn't provide a short circuit to the signal.

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Yes, this was the first thing which I felt when I saw it.
See the details on the site where I found it:

http://www.satcure.co.uk/tech/dc_inserter.htm

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