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HomeAircraftHelicopterHelicopter Main Discussion › DX7, Ducky, Just Ducky, Wunderful Mods Like "ON" Lamp Newly Installed
11-16-2014 06:22 PM  4 years agoPost 1
icanfly

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ontario

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Figured my DX7 could use a much slicker antenna like those on walkie talkies and wireless routers and other specialized radio equipment. All I need here is a separate receptor for the screw on antenna and either a internal antenna wire with a jack on it (have) or to use the original wire coming from the radio board.

pic shows near finished lengths and you know how far the original antenna sticks up, wasteful packaging would be needed to house the antenna end.

Shorter, removable for transport thus more compact, easier to replace, Bet ya never thought how cool it would be to have a router antenna on your tx rather than the fugly stick like old fm radios, get with the future, the DX9 is not bad, I'm really hating the antennas that stick up like mine, that's how it is. Will have to hack off the finned part sticking up from the original tx housing to sink it in all the way.

What do you think of those wlan 2.4g booster antennas?

Anyone know the db output of the original? They have signal boosters for home routers, I was thinking of attaching two antennas rather than the single one, I suppose the range increase might better but signal diversity would be stronger.

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11-16-2014 06:54 PM  4 years agoPost 2
Aaron29

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USA

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Careful. You might be getting close to busting some FCC regs. Output is capped by reg.

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11-16-2014 07:01 PM  4 years agoPost 3
Heli 770

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USA.

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Are FCC regs. good in Canada?

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11-16-2014 07:01 PM  4 years agoPost 4
dkshema

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Cedar Rapids, IA

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I was thinking of attaching two antennas rather than the single one, I suppose the range increase might better but signal diversity would be stronger.
You would suppose incorrectly. Since you know little about electronics, you would be best served by leaving your transmitter alone. It's not broke and doesn't need fixing.

Simply adding another antenna does not improve operation or range. And "diversity" gets no better, either.

-----
Dave

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

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11-16-2014 07:06 PM  4 years agoPost 5
Aaron29

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USA

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ok maybe not FCC
But I can't imagine there aren't similar international standards.

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11-16-2014 10:13 PM  4 years agoPost 6
Heli_Splatter

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USA

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most important aspect of antenna design is frequency. Changing the length of the antenna wire might burn out the RF section of the transmitter and will greatly affect the transmission distance.

Antennas are matched to the transmitter and calibrated. If you do not have those measurement tools, you are shooting in the dark and can damage the transmitter. Yes dual diversity antenna design is a good thing and you will see it in the newer Dx8, DX18, DX9 designs. There are actually two cross polar antennas and the remaining antenna does not fold. Each antenna works separately as if it is the only one.

Getting more distance is a function of radiated power, and this is where you will get in trouble with the FCC. If you really need the extra range, you will have to look at different frequencies and will likely need a ham license to use them.

If you want to pursue this topic, you should pick up some amateur radio manuals and start reading.

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11-16-2014 10:47 PM  4 years agoPost 7
icanfly

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ontario

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I don't know if anyone has their antennas crossed or what but I would not have any desire to modify the signal reception length or it would make the tx useless.

I since destroyed one of the pictured detachable antenna and the very same 2.4gig length wire that's on your rx's are what is inside the tx one, I knew that. I got the antenna I sacrificed off an old walkie talkie or cell phone.

In case you might be wondering, I did mess with fine electronics some time back as I worked for an electronics and motherboard manufacturer for a short while. I'm not baby at this shyt, in fact I would design a whole new tx from scratch if I had my way and will probably gut one as a donor for a mock up, working. This little tx mod is nothing in my book except an improvement.

Camon you experts, tell my how many db you loose per cm of receiver wire length, not the unshielded whip of 30.5mm.

How do you like the name it's know as irl,,,,,, the "RUBBER DUCKY" antenna, lol.
Output is capped by reg.
hmm, output equals range? What does that say about laptops and bluetooth? Are they regulated to the manufacturer? Output, now there's a factor worth noting.

holee crap, I just did a search on the innards of a rubber duckie and wow, do you know it's a half wave dipole with the ground as the other half of the 1/4 length inner wire. Do you know about a parabolic reflector and increased signal focus and clarity? Forget the booster, the reflector can increase signal reception by 24db, man, so much to learn, hehe.

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11-17-2014 02:29 AM  4 years agoPost 8
EEngineer

rrProfessor

TX

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holee crap, I just did a search on the innards of a rubber duckie and wow, do you know it's a half wave dipole with the ground as the other half of the 1/4 length inner wire.
Yes, at 27 MHz.

Things work differently at 2.4 GHz

Without a network analyzer, you're working in the dark.

And having no experience at microwave RF frequencies doessn't help either.

FWIW

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11-17-2014 02:36 AM  4 years agoPost 9
EEngineer

rrProfessor

TX

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ok maybe not FCC

But I can't imagine there aren't similar international standards.
Like this:

http://www.crtc.gc.ca/eng/home-accueil.htm

Plus, they have agreements with the FCC:

http://transition.fcc.gov/ib/sand/a..._frequency.html

FWIW

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11-17-2014 02:39 AM  4 years agoPost 10
Jim Cimino

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NE Pennsylvania

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My Graupner MC-20 doesn't have an antena.

Team Synergy, Team Scorpion, No good deed goes unpunished

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11-17-2014 02:45 AM  4 years agoPost 11
EEngineer

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TX

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Antennas are matched to the transmitter and calibrated. If you do not have those measurement tools, you are shooting in the dark and can damage the transmitter.
Antenna systems are designed to radiate most of the power with little reflection.

Your modification, rather than radiating more power, could result in reflecting that power back toward the RF output IC....and in the end, destroy that IC.

In fact, one can obtain a dead short at particular frequency using the right length of antenna.

Are you familiar with transmission line RF theory?

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11-17-2014 02:46 AM  4 years agoPost 12
EEngineer

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TX

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But I admire your industriousness....

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11-17-2014 02:48 AM  4 years agoPost 13
icanfly

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ontario

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all the info I'm reading and people still say it's a dark science.

Found a good article on range and db. Seems the rc tx's we all use are limited to 100mw.

The new Futaba 10j has no protruding antenna, that's easy to do just by taking a short antenna for a rx with the gold plug at one end and plugging it into the board, while taping the lick into the inside of the tx case. Or how about those small pc stick board antennas? crazy the old stand up stick poker antenna could be cut off completely.

I'm due for a change to either the dx 8 or 9 soon. I don't see where there's a multiple antenna on those, I see just one poker on the tops of the 9 and 18.

An article found on a search says multiple antenna are better than a single boosted one, never mind going that far with the 7. +12db is about 4km of range btw. 100mW nets about 1km so I suppose if you had two antenna at 100mW each (a go around) you'd get 2km of range.

As long as exactly 3.7mm of expose internal coax wire is on the tx and rx then they are signal matched to the 2.4gig tx as per the original manufacturers specs.

I'd like to see someone post a pic of the inside of an broken dx6,7,8 tx antenna (don't wreck a new one if you don't have to).

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11-17-2014 02:48 AM  4 years agoPost 14
EEngineer

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TX

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My Graupner MC-20 doesn't have an antena.
No antenna...no transmission nor reception....

What your MC-20 has is an antenna that is built into a PCB assembly.

Which only works at such high frequencies.

FWIW

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11-17-2014 02:59 AM  4 years agoPost 15
icanfly

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ontario

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title should have said "substitution" rather than mod.
As long as exactly 3.7mm of expose internal coax wire is on the tx and rx then they are signal matched to the 2.4gig tx as per the original manufacturers specs.
this is so absolutely wrongo it's not funny. Took the rubber end off my dx7 antenna to reveal a dipole one similar, the SAME, as the removable one I'm planning to switch to. The dx7 whip has a 26mm with a negative polarity tube attached to it, show ya pics tomorrow. In an article read tonight the dude talked about this half wave 26mm coax aspect. RF is an area not spent much time on yet, goonna be a loooooong winter with plenty time to read up.

the old am/fm systems were a very good deterrent to my becoming interested in anything rc before 2.4, fly aways and all.

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11-17-2014 04:29 AM  4 years agoPost 16
EEngineer

rrProfessor

TX

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all the info I'm reading and people still say it's a dark science.
What's a "dark science"?

Haphazardly modifying your engineered TX antenna?

What electrical equipment are ya'll using to quantify
your "improvements"?

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11-17-2014 04:31 AM  4 years agoPost 17
EEngineer

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TX

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Are the articles you mention written by 2.4 GHz antenna engineers or by hobbyists with a website?.....

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11-17-2014 04:37 AM  4 years agoPost 18
EEngineer

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TX

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An article found on a search says
As long as exactly 3.7mm of expose internal coax wire is on the tx and rx then they are signal matched to the 2.4gig tx as per the original manufacturers specs.
That's quite the precise measurement technique....

I'd be very skeptical.

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11-17-2014 04:47 AM  4 years agoPost 19
Aaron29

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USA

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Biggest thing I want to know, is when and where will this radio be activated, and what's it's range, so I can ground my stuff if necessary when this experimental radio is turned on!

Make sure you win friends and influence people by NOT shooting them down.

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11-17-2014 04:52 AM  4 years agoPost 20
EEngineer

rrProfessor

TX

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The US FCC has agreements with the Canadians with regards to minor issues close to our borders.

Can't prevent someone from doing what they might do, without having much insite of what they are doing.

Hope no one else is hurt.

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HomeAircraftHelicopterHelicopter Main Discussion › DX7, Ducky, Just Ducky, Wunderful Mods Like "ON" Lamp Newly Installed
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