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HomeAircraftHelicopterHelicopter Main Discussion › RX modification, Long Antenna Change
02-22-2013 03:21 AM  5 years agoPost 1
icanfly

rrElite Veteran

ontario

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So I want to add a longer antenna on my rxs from now on, I have Spectrum rxs with two antenna, and some shielded antenna wire from old laptop computers.

The big question is, Where does the shielding go at the rx? Ground? Nothing? Where's the grounding on the rx?

So imagine a rx antenna wire but with a braided wire cover and plastic jacket. I've peeled back the braid enough to expose antenna wire same length as the original rx wire. This will route further away from the chassis.

I haven't done enough internet searching yet, would like to know what other heli builders have done.

(pic coming)

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02-22-2013 03:50 AM  5 years agoPost 2
dkshema

rrMaster

Cedar Rapids, IA

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Before we jump into the discussion about the pros and/or cons of doing what you wish, the obvious question is "why?"

To what end do you believe you need to have longer antenna wires on something that works perfectly well in its stock form?

The adage "if it ain't broke, don't fix it" comes to mind here.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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02-22-2013 03:55 AM  5 years agoPost 3
HeliOCD

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San Diego, CA

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I dont think he wants a longer antenna but a longer feed line to route the antenna in a different place. Still having the same length antenna wire. Just longer feed to it.

Its all earth!

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02-22-2013 04:00 AM  5 years agoPost 4
HeliOCD

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San Diego, CA

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Just understand that microwave loses power very easy when length and connections are in play. Remove original wire from pcb and use microwve shielded wire up to the termination point, which should be kept within reason.

Its all earth!

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02-22-2013 04:18 AM  5 years agoPost 5
dkshema

rrMaster

Cedar Rapids, IA

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May not have been clear in my reply, but I did understand the intent to extend the current antenna wires, similar to the Futaba design, or the Spektrum carbon-fiber fuselage receiver designs.

To simply add "longer" antenna wires would be detrimental.

Still, I don't see the need to do what the OP asked in the first place.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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02-22-2013 04:27 AM  5 years agoPost 6
HeliOCD

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San Diego, CA

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He may be making a new stealth high tech heli. To each his own..

Its all earth!

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02-22-2013 11:41 AM  5 years agoPost 7
icanfly

rrElite Veteran

ontario

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What I'm trying to do is similar to Traxxis rx's with a longer feed line, the actual antenna stays about 3cm long and is the microwave shielded wire.

Why, To extend the rx set of antennas a bit further out from the frame/cf and be able to put a satellite near the battery but route the antenna away from it.
He may be making a new stealth high tech heli.

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02-22-2013 03:03 PM  5 years agoPost 8
jgunpilot

rrKey Veteran

Pollock, LA

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Call the radio manufacturer and see what they recommend you do with their carefully designed product. I'll be they tell you to leave it alone.

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02-22-2013 04:23 PM  5 years agoPost 9
GetToDaChopper

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Las Vegas , NV

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As far as i know antennas are set at a "tuned" length that you don't want to mess with, also someone correct me if i'm wrong aboyt this but Spectrum rxs have one antenna is the ground and the other is not (i don't really want to say pos)......

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02-22-2013 04:45 PM  5 years agoPost 10
Four Stroker

rrElite Veteran

Atlanta

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You cannot do what you are asking. Other brands have a 50 ohm trace terminated in a U.FL micro coax connector and you can indeed put a longer antenna on there.

You only bet might be to find a clone receiver that does use a micro coax connector - Orange, Blue, Green - and then use anyone's replacement antenna.

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02-22-2013 04:48 PM  5 years agoPost 11
Andy from Sandy

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Bedfordshire, UK

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I think the way Spektrum have done it the wires form a dipole so both bits of wire is one antenna and you cannot change their length or proximity to each other.

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02-22-2013 11:12 PM  5 years agoPost 12
icanfly

rrElite Veteran

ontario

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Have you seen the Spectrum ar500? http://www.google.ca/imgres?imgurl=...ved=0CDkQrQMwBw

It has a long lead wire with the prescribed 3cm non shielded end. Can it be so hard to mod any rx like that?

Some people don't worry about failure, without experimentation and trial nothing would be what it is today. I'm not doing anything outside the box, only want to extend the antenna section of wire outside the box (of heli cf, batteries, naughty bits).

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02-22-2013 11:29 PM  5 years agoPost 13
qraptor

rrApprentice

Illinois

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Here is an idea for you:

http://www.keenansystems.com/store/...products_id=173

It is 10 inches long, and you could snip the TNC connector off. It should give you a long enough lead, I think.

Hope your experiment works out. Please keep us posted.

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02-22-2013 11:57 PM  5 years agoPost 14
icanfly

rrElite Veteran

ontario

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The thin wire in the foreground of the link is what I have plenty of.

I'm thinking the shielding needs to be grounded to the system in order to attract static.

Look, you could run one of these right through the tail tube out the back end of the heli if you wanted to, but you don't need that much isolation.

As it stands most rx antenna are ok.

I want more versatility with antenna placement, like I had a cf canopy and want to run the antenna outside the shell. The existing antennas on (most) Spectrum rxs have no lead so they wouldn't work.

Yea, it's gotta be like the Futaba fasst system antennas with long leads.

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02-23-2013 01:18 AM  5 years agoPost 15
GetToDaChopper

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Las Vegas , NV

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Yea, it's gotta be like the Futaba fasst system antennas with long leads
But futabas FASST system ants are dif than spektrums like what Andy from Sandy said in that spektrum have done it were the wires form a dipole But futabas is a two antenna diversity system, way dif than spektrums system.......

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02-23-2013 02:20 AM  5 years agoPost 16
icanfly

rrElite Veteran

ontario

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spektrum have done it were the wires form a dipole
Like "Rabbit Ears" on an old cr TV set.

Looks like I will have to try something out with an extra rx I have, cant be all bad as the extended feed ant's will still form a dipole.

Not to worry, a member pm'd me about a system worth looking into based on accst, "Advanced Continuous Channel Shifting Technology", aka frequency hopping. Range is massive (3 miles) and needs nothing extra like a satellite.

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02-23-2013 05:37 AM  5 years agoPost 17
GetToDaChopper

rrElite Veteran

Las Vegas , NV

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"Advanced Continuous Channel Shifting Technology", aka frequency hopping. Range is massive (3 miles) and needs nothing extra like a satellite.
Ya i have one now it's called a Futaba FASST system, the Range is massive, farther than you can see !!!

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02-23-2013 04:59 PM  5 years agoPost 18
ThumbBumper

rrVeteran

A little to the right and down!

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Bad idea....

A couple of things to consider:
1. Even changing the length of the antenna as little as 1/8" can have a pronounced effect on the sensitivity of the receiver. These are 1/4 wavelength antennas that are cut for 2.4Ghz

2. Adding coax between the antenna and the receiver introduces loss. Depending on the coax used, you can seriously attenuate the signal captured from the antenna and delivered to the receiver further reducing receiver sensitivity.

3. Finally, depending on how you make the physical connection, you can seriously change the impedance (electrical resistance) of the antenna and it's feed line. Doing so again can seriously reduce the signal that is delivered to the receiver and adversely effect receiver sensitivity.

In all honesty, if you have a very good reason for wanting to do this, you might be better off with a spectrum receiver and a couple of satellites. The interconnecting wires from the satellites to not carry RF and could theoretically be lengthened much easier and safer than trying to modify the RF side of the receiver.

My $0.02...
Good Luck,
Bob

If it ain't broke, go fly some more!
http://facebook.com/groups/TORCHS/

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