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HelicopterRadio - Spektrum DSM › Spektrum DX7 ... Good Radio except!
08-09-2007 07:38 PM  10 years agoPost 1
n55w131

rrNovice

Ketchikan, Alaska

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I like my DX7, I have 3 AR7000's in 3 helos. Recently I broke my antenna. Guess what, you can't buy a replacement. A simple single screw and 5 minute fix and yet you are forced to send your radio in to Horizon, pay their minimum labor rate, and wait 3 weeks for your radio to come back.

Not acceptable to me!

I think I should have stayed with Futaba and purchased their new 2.4ghz radio. At least you can order spare parts for it.

In the mean time, I super glued the weak plastic base back on. Guess I live with it till winter comes along. Wait. Guess what! I found a replacement for the 2.4ghz antenna. Yep sure enough its a specktrum under the hood, only cost me $15. Yep I voided the warranty by doing so. (I did a 1/2 mile range check just to make sure there were no issues.)

If anyones interested I'll let you know when I post my DX7 and 3 AR7000's on ebay. Summers almost over so i am going to fly with what I have for now.

Live / Crash / Learn

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08-09-2007 10:05 PM  10 years agoPost 2
Al Austria

rrElite Veteran

Gainesville, FL

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How did you break your antenna?

I love my DX7!

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08-09-2007 10:14 PM  10 years agoPost 3
Micro-Maniac

rrElite Veteran

Pasco,Washington​Formerly: Captain​Chaos

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Hmm - The BCX2 2.4ghz radio antenna looks the same to me

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08-10-2007 12:17 AM  10 years agoPost 4
n55w131

rrNovice

Ketchikan, Alaska

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Replacement antenna.

Yes the Eflite CX2 replacement antenna will work, That is what I used, however the mount post is about 1/8" longer so the metal plate and screw do not lock properly. Also the antenna wire itself is approx 4" longer than the DX7 original. Not quite sure which length is correct (both operate on the exact same frequencies). All antenna's and the wire length combined are supposed to match the frequency. (Not going into a buch of detail about this). That is why I did the 1/2 mile range check. It works ok with the AR7000 but I am not sure I would trust it with any other receiver that does not have a remote.

Still dissapointed I can't just buy the antenna. I could understand their position if I was asking for a pc board or something that might need calibration or tuning, but the antenna is a simple plug-n-play device.

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08-10-2007 01:11 AM  10 years agoPost 5
Micro-Maniac

rrElite Veteran

Pasco,Washington​Formerly: Captain​Chaos

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I think it's strange that they do offer the antenna for the CX2 but not the DX6/7 as I don't see any difference in replacing an antenna on a DX6/7 radio than on a CX2 radio

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08-10-2007 07:26 AM  10 years agoPost 6
n55w131

rrNovice

Ketchikan, Alaska

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How did it break?

Al Austria-

Well my daughter goes flying with me, she takes the stills and videos. And she picked up the radio by the antenna to hand it to me, and snap! She didn't know it was so fragile and I wasn't watching when she picked it up to say something. My fault.

Micro-Maniac-

Exactly, its a simple replacement. Heck they let you go inside to change the soft slider to the ratching type on the throttle stick so opening the case sure isn't the issue. Go figure.

Perhaps Paul Beard w/Spektrum could jump in here and give us an answer. I know he follows these posts about the DX6/DX7.

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08-10-2007 12:25 PM  10 years agoPost 7
SRH990

rrKey Veteran

Birmingham, UK

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In the UK Inwoods are selling a replacement antenna for the DX7, I had one delivered yesterday, cost around £5/$10. It arrived in a plain plastic sheath but is identical to the original except the coax lead is slightly shorter.

Steve -Trex 700N, Trex 600N, Raptor 550E, 450SE, Mini Titan, Logo 5003D, Beam E4

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08-10-2007 05:55 PM  10 years agoPost 8
midwestpilot

rrElite Veteran

Crystal Lake, IL

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glue it back

that is what I would do until winter and then send it in

In life there is no spacebar!

Rich Erikson AMA 6175

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08-13-2007 09:15 AM  10 years agoPost 9
Corona44

rrApprentice

Sydney,NSW Australia

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I had no problem buying a replacement antenna for my DX7 here in Australia (knocked it off the desk onto the floor) and it was reasonably cheap as well.

Flying, crashing & having a ball.

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08-13-2007 04:49 PM  10 years agoPost 10
teamdavey2001

rrApprentice

Sunnyvale,​California, USA

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(Also the antenna wire itself is approx 4" longer than the DX7 original. Not quite sure which length is correct (both operate on the exact same frequencies)."

That's not a wire it's a coax so the length is immeterial except for a tiny difference in attenuation (loss).

As long as you didn't destroy the connector replacing the antenna and the range checks out OK (mine beat the 30 paces by a large margin) you should be good to go.

Jim Davey

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08-13-2007 06:28 PM  10 years agoPost 11
n55w131

rrNovice

Ketchikan, Alaska

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Wire (Coax) length!

Jim,

Sorry but it is material. And it can be more than just a tiny loss. It can also cause TX/RX failure. The antenna, antenna wire (coax) and connector combined determine the actual wavelength and the SWR of that combination. If they do not match you will reduce your effective radiated power resulting in range loss. The mismatch can also cause damage to a transmitters finals. If you would like to learn more about antennas, coax and TX/RX transmission I can suplly you with lots of refence web sites. http://www.arrl.org is a good starting place. The publication "The ARRL Antenna Book" is a good start.

Cheers,

Rick Watson

WL7XG
AMA 245281

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08-15-2007 12:48 AM  10 years agoPost 12
n55w131

rrNovice

Ketchikan, Alaska

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Specktrum / Horizon Support!

I have been informed by Horizon that a direct replacement antenna has been shipped to me today. No charge for the Antenna or the Shipping.

In this case Horizon (Spektrum) has come through for me. If this is a true indication of how all specktrum customers will be treated then I take back everything I have said as one could not find better support.

Thank-you Horizon.

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08-15-2007 10:04 PM  10 years agoPost 13
gotak

rrApprentice

Ontario, Canada

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The coax length does not matter. http://en.wikipedia.org/wiki/Transmission_line

"It's a diagram of my idea I don't have no freaking equations yet"

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08-16-2007 12:29 AM  10 years agoPost 14
n55w131

rrNovice

Ketchikan, Alaska

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Gotak, Sorry but you are wrong!

I suggest you do some more reading before you make such an incorrect statement. The transmission line is very important!

In your quote from the wikipedia you can find the true answer if you just read a bit further than the first sentence. The second sentence explains "Stated another way, the length of the wire is important when the signal includes frequency components with corresponding wavelengths comparable to the length of the wire."

Do you know what frequency components are?

Just curious? Do you know what WL7XG stands for?

I can tell you that it did take a bit more than reading the first sentence of the wikipedia to obatain it.

Do you know what AMA# 245281 is?

I can tell you I did not just obtain that number yesterday.

I appologize to other readers but I get a bit flusterd when some wannabee's complicate things by jumping into the middle of a subject they know nothing about.

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08-16-2007 07:40 AM  10 years agoPost 15
Discharger

rrApprentice

Perth, Western​Australia

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No need to get flustered WL7XG!
Great to see antennas still causing heated discussions!
Depends on the design of the antenna, If the actual radiator impedence is matched to the coax and the output is the same impedence then it is a flat line and the length is not so important except for line losses which may be high at gHz,
If on the other hand the design is such that the coax is a tuned line together with the radiator then the length of the coax will be important in order to match the output. I've not played around with microwaves but I would imagine quite probably quite lossy at these frequencies though I would think what say you WL7XG?

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08-16-2007 03:41 PM  10 years agoPost 16
Rick_H

rrKey Veteran

Boulder City, Nevada

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I broke the antenna on my DX6 and sent it in to be repaired, All it cost me was the shipping charge. They covered the repair costs even though it was my fault it broke.

Rick

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08-16-2007 04:59 PM  10 years agoPost 17
teamdavey2001

rrApprentice

Sunnyvale,​California, USA

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Never mind - Discharger said it all.

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08-16-2007 06:51 PM  10 years agoPost 18
n55w131

rrNovice

Ketchikan, Alaska

My Posts: All  Forum  Topic

Correct!

Thank-you Guys for the replys. Again, I do appologize!

Sorry, not really heated, just a bit flustered. I have sat back and watched people offer suggestions here, which is great, but a bit annoying after you find out they don't eveny own a helicopter or an RC radio for that matter.

About the antenna thing. We all strive for performance, nobody want's to loose their helo due to a radio problem. Its bad enough when its other mechanical failure or even just a plain my fault crash. Hence the concern over a modified (eflight blade CX2 anntena) DX7 radio where there is a significant difference in coax wire lengths (say 4" or more). The range on the CX2 is only 500ft. (This of corse is power output related) But it could also be of concern if the antenna is used on higher power transmitters. Knowning that two different lengths of coax can not be correct, unless they are matched, this of corse can be done mechanically by cutting the coax to the correct length, or electronically by using coils as antenna trimmers.

In any case, my point was in-fact that an impropperly matched transmission connector, coax and antenna can result in reduced range and possible transmitter damage.

I have a very expensive AEA antenna analyzer that I use on VHF and UHF but it does not work on 2.4ghz or I would be providing factual proof of each combination for us to look at. Without that we could still do the math if we measure the length of the two combinations and see what frequencies the two are actually cut at.

I think the key component here is Math. As long as the math works out to the operating frequency, and this can be done at the board level with adjustable coils, at the transmission by line length, at the base, mid or top section of the antenna by loading, or by an adjustable length tip to fine tune the transmitters output for the lowest possible SWR, will result in maxium power output and range. Another factor is line loss due to poor quality connectors, coax, or construction.

Cheers.

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08-16-2007 07:10 PM  10 years agoPost 19
teamdavey2001

rrApprentice

Sunnyvale,​California, USA

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A few minutes on the internet checking the specs for these antennas might provide you with a few facts as to their characteristics and plug and play nature.

You might also throttle back some of the condescension in your posts. Some of us out here actually do know what we are talking about.

Membership of the ARRL (remember what the first letter stands for) does not automatically confer wisdom and a low AMA number just says you have been playing with toy aeroplanes for a long time

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08-16-2007 08:03 PM  10 years agoPost 20
sharam

rrElite Veteran

Northern California​- Fly at Morgan Hill​Field

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When teamdavey2001 says, "jump", my only question is, "how high?"

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