DIAMOND D777 IN LOFT?

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Re: DIAMOND D777 IN LOFT?

Postby G4RMT » Mon Dec 31, 2018 3:27 pm

The clue is in the no gain, and in one of them described as parallel quarter waves. Essentiall multiple ¼ wave antennas joined at the bottom. Personally the 777 would perform better than all of those, and have a bit of gain in some areas.
Last edited by G4RMT on Mon Dec 31, 2018 4:09 pm, edited 1 time in total.
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Mon Dec 31, 2018 3:42 pm

G4RMT wrote:The clue is in the no gain, and in one of them parallel quarter waves. Essentiall multiple ¼ wave antennas joined at the bottom. Personally the 777 would perform better than all of those, and have a bit of gain in some areas.

I think ill get the scanmaster, just been again in loft with cheep telescopic and it gets 3 bars for all scottish controls, so a antenna up there will definitely preform well. D777 isnt needed for good signals. Now just question of airband specific or wideband (scanmaster) The wideband is longer, and from my telescopic , the longer seems generally better for airband as it reaches a higher verical height. Any suggestions?
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Mon Dec 31, 2018 3:49 pm

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Re: DIAMOND D777 IN LOFT?

Postby Chris P » Tue Jan 01, 2019 10:10 am

A band specific such as the scanmaster airmaster will be better than a wideband "white stick" If you are only interested in the civil airband .Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required . Mine was suspended from the roof timbers with the coax feed held at right angles for about 1m using tape or string . You can progress to a more sturdy version using copper tube once you have found the "sweet spot" in the loft . Moving a VHF antenna around by only a few feet can improve signals considerably .

My dipole gives me s9 signals from the chedburgh Nats site which is some 30 miles south east of me and carries Essex radar allowing me to monitor inbound traffic into Stansted . The aircraft can be received down to about 500 ft on approach but I am unable to hear the ground stations at Stansted



The other advantage is that this sort of homebrew antenna costs almost nothing to make .
If you want a wideband antenna try a bowtie made from two 800 mm pieces of stiff wire ( I use seperated 2.5mm twin and earth cable) each piece bent into a Vshape with the open end being about 340mm and the coax connected to the centre again with choc bloc, the outer to the lower V and the core to the upper V the elements should be vertical and the coax should feed horizontally away from the centre for a wavelength or so if possible
Regards Chris aka G8FFF nipper or tazmin88
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Tue Jan 01, 2019 10:38 am

Chris P wrote:A band specific such as the scanmaster airmaster will be better than a wideband "white stick" If you are only interested in the civil airband .Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required . Mine was suspended from the roof timbers with the coax feed held at right angles for about 1m using tape or string . You can progress to a more sturdy version using copper tube once you have found the "sweet spot" in the loft . Moving a VHF antenna around by only a few feet can improve signals considerably .

My dipole gives me s9 signals from the chedburgh Nats site which is some 30 miles south east of me and carries Essex radar allowing me to monitor inbound traffic into Stansted . The aircraft can be received down to about 500 ft on approach but I am unable to hear the ground stations at Stansted



The other advantage is that this sort of homebrew antenna costs almost nothing to make .
If you want a wideband antenna try a bowtie made from two 800 mm pieces of stiff wire ( I use seperated 2.5mm twin and earth cable) each piece bent into a Vshape with the open end being about 340mm and the coax connected to the centre again with choc bloc, the outer to the lower V and the core to the upper V the elements should be vertical and the coax should feed horizontally away from the centre for a wavelength or so if possible

What coax would be best? 50ohm rg213?
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Tue Jan 01, 2019 10:38 am

Chris P wrote:A band specific such as the scanmaster airmaster will be better than a wideband "white stick" If you are only interested in the civil airband .Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required . Mine was suspended from the roof timbers with the coax feed held at right angles for about 1m using tape or string . You can progress to a more sturdy version using copper tube once you have found the "sweet spot" in the loft . Moving a VHF antenna around by only a few feet can improve signals considerably .

My dipole gives me s9 signals from the chedburgh Nats site which is some 30 miles south east of me and carries Essex radar allowing me to monitor inbound traffic into Stansted . The aircraft can be received down to about 500 ft on approach but I am unable to hear the ground stations at Stansted



The other advantage is that this sort of homebrew antenna costs almost nothing to make .
If you want a wideband antenna try a bowtie made from two 800 mm pieces of stiff wire ( I use seperated 2.5mm twin and earth cable) each piece bent into a Vshape with the open end being about 340mm and the coax connected to the centre again with choc bloc, the outer to the lower V and the core to the upper V the elements should be vertical and the coax should feed horizontally away from the centre for a wavelength or so if possible

What coax would be best? 50ohm rg213?
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Tue Jan 01, 2019 10:40 am

Chris P wrote:A band specific such as the scanmaster airmaster will be better than a wideband "white stick" If you are only interested in the civil airband .Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required . Mine was suspended from the roof timbers with the coax feed held at right angles for about 1m using tape or string . You can progress to a more sturdy version using copper tube once you have found the "sweet spot" in the loft . Moving a VHF antenna around by only a few feet can improve signals considerably .

My dipole gives me s9 signals from the chedburgh Nats site which is some 30 miles south east of me and carries Essex radar allowing me to monitor inbound traffic into Stansted . The aircraft can be received down to about 500 ft on approach but I am unable to hear the ground stations at Stansted



The other advantage is that this sort of homebrew antenna costs almost nothing to make .
If you want a wideband antenna try a bowtie made from two 800 mm pieces of stiff wire ( I use seperated 2.5mm twin and earth cable) each piece bent into a Vshape with the open end being about 340mm and the coax connected to the centre again with choc bloc, the outer to the lower V and the core to the upper V the elements should be vertical and the coax should feed horizontally away from the centre for a wavelength or so if possible

How far is stansted from you?
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Re: DIAMOND D777 IN LOFT?

Postby deadite66 » Tue Jan 01, 2019 11:14 am

Chris P wrote:.Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required


yup, the marine band chocbloc dipole i made was just about the same as the MARI-1 i bought.
Airspy R2 on a Marine tuned dipole (Rocket Radio MARI-1)
24/7 Marine recording with RTLSDR_Airband
Airspy R2 on a Discone
SDRplay RSP1A on a homebrew UHF dipole
Yupiteru MVT-9000 MKII telescopic ant.
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Re: DIAMOND D777 IN LOFT?

Postby waxmax » Tue Jan 01, 2019 11:23 am

Which coax would be best for this ?
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Re: DIAMOND D777 IN LOFT?

Postby G4RMT » Tue Jan 01, 2019 12:38 pm

The object for receive is simply maximum signal. If you are only looking at VHF airband, the 'correct' answer is to look at the specs for the cables and look for the loss per metre at a frequency close to your desired one. 213 is probably the best in terms of loss, but is more expensive, thicker and stiffer. 58 I'd probably avoid.

There is a modern view that for receive only, then you can use the thinner satellite/TV antenna stuff because it's 75Ohm impedance doesn't matter. In a way, it does matter because the antenna is designed to be most effective at a fixed frequency, and the cable mismatch has an impact. The idea being that the cable plays no part in the chain, apart from passing the signal. The impedance change allows the cable itself to become part of the antenna. Not by much, but if the reason for a VSWR match is to allow everything to go one way and not get reflected, it also works in reverse, what the antenna 'captures' will go towards the receiver, but not all gets there some is reflected. The ratio with a receiver vs a transmitter is exactly the same. Transmitter impedance, cable impedance, antenna impedance all the same =. best VSWR, most efficient transmission chain. Any losses caused by the wrong cable just mean less RF. This applies to the receive chain too. The good news is it's still a small extra loss, and the very low loss of the cable makes up for it for most purposes.

The worst thing is connectors. Have you got any PL259 connectors, or N or BNC types that will fit reliably the RG6 type cable? If you bodge the connectors both ends, then you can lose more signal, and at the top end, it's difficult to keep water out unless you're very good with self-amalgamating tape. The real problem is that you have a thin drain wire and foil wrap. Not easy to get secure in a compression clamp, and if you use a PL259 connector with a side hole where you solder the braid, there is so little copper, that if you twist the cable, it can snap the thin drain wire. If you try to use tapered thread CB type connectors, then the 'grab' is terrible.

For me - despite the performance of the TV/satellite cable (and it's cost), I'd go for 213. It works. It fits connectors properly and it is tougher. RG6 is designed for F connectors, using the centre conductor and a twist on connection to the hollow F connector. You could use adaptors from F to 259 or BNC, but most of these are not wonderful performance wise. The old very low loss on connectors with gold or silver pins and decent construction hardly applies when they're knocked out in China for 50p.
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