antenna location

[sleep4]

Has anyone had or know of any reception problems with an internal antenna location in a cabon 68 fuse( ie. Pike superior)?

Thanks for any help.

[spatial]

Carbon fuses seem to cause reception problems with tx/rx on 35-36Mhz and 40Mhz. It doesn't seem to an issue for users on 72Mhz. Try searching the archives. The problem and possible solutions have been discussed quite extensively.

cheers
Paul

[Sparky Paul]

It would be prudent to have as much of the antenna outside the fuselage as you can put up with, appearance wise.
CF has the reputation for blocking the signal for the wire length inside the CF, which can reduce sensitivity.
I haven't any quantitative tests on this though.

[oakman7004]

The only way to know for sure is testing.
If there are problems there are several ways of solving them. Here is a good link with explenation/pics of some of the ways of keeping the range up.

http://www.f3j.com/antenna.htm

Good luck!
/Jonas

[OVSS Boss]

It is a problem for 72 mhz, on any Samba fuse, I have ~18" hanging out the vertical stab root free in the air. Also, go to Samba or Jo Jo's website and there are other solutions. 72 mhz will not operate optimally with the antennae internally in these fuses.

Marc

[h.eberbach]

sleep 4,

take care!
There is absolutely NO technical argument why antennae within carbon fiber fuselages should work alright on 72 MHz and not on 35/40/41/53 MHz.

Herbert

[Shortarse_Yoda]

There are currently 3 methods in use that I know of BUT regardless of what you do if you are flying an all carbon model you MUST use a DSP type receiver, Schulze, MPX etc. When range checking with the aerial fully down (1 section) you should get 50yds.

1.) Extend the reciever aerial by about 18" and feed down the fus and dangle out the back. I have flown my all carbon models at the limits of vision with a single conversion shultz dsp receiver with no problems.

2) If using X-tail feed aerial down fus up to top of fin and solder to a thin peice of piano wire around 18" long extendeding backwards from the top of the fin. This has been used by flyers europe. Make the piano wire somehow removable for transport would be sensible.

3) Route aerial down fus to just past tow-hook exit bottom of fus and let it dangle.

I must emphasise that all these solutions have been tried and tested on the european 35mhz frequencies. I know people will say 'but you cannot extend the receiver aerial, it will go out of tune.' All I can catagorically state is that I have flown my Carbon mdels using methods 1 & 3 and flown it so far away as not to be sensible with no issues.

Here in the UK a number of flyers are using these methods with no glicthes or range issues. If however you are trying to use 'normal' dual conversion or PCM receivers without signal processing technology then forget it!

Hope this helps.

[Phil Barnes]

Technical arguments have not proven to be very useful in answering the 72mhz versus 35mhz carbon shielding question. Practical experience of people who have flown both systems has proven that there is a very big difference though. You might want to read this thread (http://www.rcgroups.com/forums/showthread.php?p=4870286#post4870286).

In practice 72mhz RC systems are far less affected by carbon shielding than are 35mhz systems. It is quite common in the US where we fly on 72mhz to run reciever antennas inside carbon booms. Guys who fly on 35mhz need to be far more careful to avoid carbon shielding. 72mhz systems do suffer some loss of range from carbon shielding but in the vast majority of cases there is still plenty of range left to safely fly the model.

There is significant evidence (from practical experience, not from theory) that fuselages made from the carbon/kevlar hybrid fabric are especially bad in terms of carbon shielding. The Pike fuselage is probably made from this fabric. many of the modern molded sailplanes use this fabric for the fuselage and even 72mhz systems have been known to have serious problems with those models when the reciever antenna was installed completely inside the fuselage/tailboom.

[glidagida]

Hi S4

Just coincidentally I am putting a new full Carbon Corrado 2000 'V' tail [called Zenith in the States] together and I went out and range checked the gear this evening. This model uses a Schulze 36 Mhz receiver and Graupner MC22 transmitter.

I have a 400mm [16"] piano wire extension suggested by a friend coming out in the middle of the 'V'.

With the model on the ground [worst case scenario] and the transmitter antenna collapsed I managed 185 metres.

With the whip extension removed the range reduced to 125 metres, about a 30% reduction.

With the model with the fuselage positioned vertically the range increased to 209 metres.

No science, just a comment from the practical side.

Cheers
Dave

[Sparky Paul]

I'm thinking of putting another receiver (on a different 72 Mhz channel)into one of my Kadets, and have it control -something-... with its antenna totally inside a CF tube.
Fly it up with the usual equipment, and see if the -something- the 2nd receiver controls fails/glitches/ whatever, from close up to way out there.

[Jurgen]

With the model on the ground [worst case scenario] and the transmitter antenna collapsed I managed 185 metres.This is awesome, maybe i try a schulze for that!
Jurgen.

[Jurgen]

There are currently 3 methods in use that I know of BUT regardless of what you do if you are flying an all carbon model you MUST use a DSP type receiver, Schulze, MPX etc.With DSP you mean Digital Signal Processing i presume?
Jurgen.

[POF]

Anybody tried to connect the antenna to the carbon fuse itself? Probably difficult to get a good connection. (Don't try theory on that one;O))

[jojoen]

Anybody tried to connect the antenna to the carbon fuse itself? Probably difficult to get a good connection. (Don't try theory on that one;O))
No but before I got good RX's (some years ago) I grounded (negative) the fuse and wing on a Ariane F3B model. It helped a lot.

[Shortarse_Yoda]

Yes Jurgen Digital Signal Processor. In my experience the Shulze has the edge of the MPX IPD here in Europe. I nearly tried a MPX DS 7 Synth in my new model but bottled out at the last minute (+Shulze is 40 euro cheaper, but it does use xtals). Unless you fly JR The shulze for the money is really unbeatable.

Cheers SY.

[jojoen]

The Shulze is nearly the same as Multiplex IPD 7channel on 35mhz. One can use both in a Pike with ok results. But it is nowhere near the Multiplex IPD DS 9channel. This is probably the best non PCM receiver in Europe. I am only talking crystal versions here. Have not tested the new synth receivers. But I know they are dangerous in motor models on the ground as they can go bananas with GSM phones ringing or even just changing bases.
But with SPCM the JR 770 (Graupner SMC14) and their bigger brothers are extremely good receivers. But they need a JR/Graupner SPCM transmitter.

I also have JR 770 on 72mhz and will soon have a SMC14 on 35mhz to test against each other. A friend of mine flies the SMC14 with good results.

[Jurgen]

I bought the 'Multiplex Synth DS IPD' 2 days ago for my glider so i don't expect any motor upset. Will install it next week or so. I doubted over the Schulze but wanted to get rid of crystals for some reason. Jojo, i suppose this GSM interference is only when model is close to the GSM (on the ground) and not in flight ?? And hopefully the DS (double super) function is able to take care of that.

Seems BMI is producing/selling the successor of the Schulze technology. Rumours say Schulze lost the race (of Berg technology or something like that) and BMI got the rights now. 2TX's on same channel and still no servo-freak show, only slower movements. The Rx will 'recognise' the TX-identity and filter to that signal. And only for 54 euro's here, but yes crystals again.
Jurgen.

[jojoen]

I bought the 'Multiplex Synth DS IPD' 2 days ago for my glider so i don't expect any motor upset. Will install it next week or so. I doubted over the Schulze but wanted to get rid of crystals for some reason. Jojo, i suppose this GSM interference is only when model is close to the GSM (on the ground) and not in flight ?? And hopefully the DS (double super) function is able to take care of that.

Seems BMI is producing/selling the successor of the Schulze technology. Rumours say Schulze lost the race (of Berg technology or something like that) and BMI got the rights now. 2TX's on same channel and still no servo-freak show, only slower movements. The Rx will 'recognise' the TX-identity and filter to that signal. And only for 54 euro's here, but yes crystals again.
Jurgen.
Yes interferrence is only on the ground so no problem for gliders. But imagine a big prop on a gas engine....
BUT the synth EVO Tx is also influenced by GSM mobiles. I had to wrap my module in alufoil. Mostly using JR9303 now luckily. No problem there.

Two Rx's on same channel will not work. There is no way to "recognize" the Tx without a digital signature from the Tx (PCM/SPCM). Atleast I have no big hopes for what they say. Maybe I am wrong...

[Jurgen]

The BMI system: I think its not the purpose to use 2 on same channel, only to minimise the freaky results on the servo's to avoid a crash, time will tell, they promise alot indeed in PPM.

[jojoen]

There is one thing some of the new synth systems can do. That is that they can look at your frequency and lock on to the excact frequency. Most radios are 1-3mhz of center and that the receiver can be programmed to "learn" means that it will perform better + get rid of unwanted signals that are nearby (2-3mhz the other way).
But if two radios have the same peak it will not see the correct one. 70-80% of the radios are very accurate. We scan 100+ radios each winter on a motorevent and thereby have atleast some idea about performance on different radios.

[jojoen]

Today I flew a Supra glassfiber and had the antenna in the midsection. From the 9 pin plug I had two ends. One to the end of the midsection and one to the servo bay. The Rx was a JR770 on 72mhz and was placed under the servos. Did not do any ground tests but was probably 7-800m out (2300-2600ft). The Rx was set to go full crow if I was too far. Never experienced anything. While I was out there I both had the Tx on the ground and pointing different ways. Again no problem.
Remember this is a GLASS midsection. It will NOT work well if it were all carbon.

[aragon]

Here in the UK a number of flyers are using these methods with no glicthes or range issues. If however you are trying to use 'normal' dual conversion or PCM receivers without signal processing technology then forget it!
I saw your post and really felt the need to point out the bad in this advice.

What you're saying could be likened to saying it's ok to walk through fire, but make sure you're wearing fire proof boots. Terrible advice. While the boots may keep you from getting burnt, you should put the fire out first! If you HAVE to use DSP to get your radio behaving reliably then you should not be flying! DSP is not there to patch a poorly setup radio installation, it's a safety net for unexpected interference.

If a system does not pass a range check with DSP disabled it should not fly. Multiplex purposely give their receiver users the ability to temporarily disable IPD to aid them in range testing without IPD intervening.

[Jurgen]

In my case (full carbon Zenith) flown nearby harbor environment (lots of companies and harbor radio use) and high tension cables around everywhere, the last of glitches (after finding out best antenna solution) had to be filtered out by DSP, although ground range was pretty good. I tend to believe the air i fly in is quite poisoned with HF dirt.

Jojoen, how did your antenna solution in the mid section work out? In the end your antenna is a little parallel to the carbon spar.

Jurgen.

[jojoen]

In my case (full carbon Zenith) flown nearby harbor environment (lots of companies and harbor radio use) and high tension cables around everywhere, the last of glitches (after finding out best antenna solution) had to be filtered out by DSP, although ground range was pretty good. I tend to believe the air i fly in is quite poisoned with HF dirt.

Jojoen, how did your antenna solution in the mid section work out? In the end your antenna is a little parallel to the carbon spar.

Jurgen.

Th emidsection antenna have worked out well. But I am now receiving a carbon wing also so I have taken the antenna inside the fuse and out the back leaving 30cm to dangle. Works great that too.

One important thing guys:
It is not the signal prossesing that makes a Rx have good range. That is only a gadget that makes the jittering go away. What makes a Rx good is how they are designed in th RF part. And some of these GOOD receivers happen to have IPD, SPCM, etc...
I am talking general here.
I have tested some old Futaba and Multiplex PCM receivers. They are crap. So didgital signals does not help.

[jojoen]

...snipp...
I also have JR 770 on 72mhz and will soon have a SMC14 on 35mhz to test against each other. A friend of mine flies the SMC14 with good results.

Not yet tested in air but I did ground checks on:
JR770 72mhz versus the Graupner SMC-14 on 35mhz
These receivers are supposed to be the same but on different bands.
I tested them in the same Supra fuse and have a 1mm gold connector so I could switch with the same antenna coming out the back leaving 30cm hanging free.
There is no doubt that the 72mhz receiver gives double range compared to the 35mhz. Still I was happy about the range with the 35mhz.

This is NOT a scientific test but the best I can do atleast.

[mlee8249]

My experience with this is similar to what Phil Barnes has noted. Currently, I am running my 72-mHZ radio antennas inside the fuselage of both the Lazurite and the Fazer. Both use the carbon/kevlar fabric mix, and neither has had a problem at any range. However, on my Onyx L, which has a pure carbon tail boom, different story. I could not get a really good range check without running the antenna outside of the boom. So, this radio antenna exits out just behind the TE of the wing saddle and runs along the top of the boom, taped in place. No problems. All of my receivers are Hitec dual conversion or JR PCM type.

The bottom line I have is no matter what you have to do, make sure it's safe and works great Anything less is asking for trouble. If you don't want to try yourself, talk someone else into doing it to their plane first...if they crash, don't do what they did.

Mike Lee

[sleep4]

Just heard from Gordy Stahl who is a carbon fuse Pike guy. He also recommends getting the antenna out of the fuse to avoid danger. He says carbon Pikes are particularly not "inside the boom friendly" when it come to antenna positioning.

[Tuomo]

Just heard from Gordy Stahl who is a carbon fuse Pike guy. He also recommends getting the antenna out of the fuse to avoid danger. He says carbon Pikes are particularly not "inside the boom friendly" when it come to antenna positioning.

I do not see why Pikes would be any different from other current F3J/B planes. Almost every manufacturer uses similar carbon/kevlar hybrid structure.

Jo's test on 35 vs 72 Mhz is very interesting. I wonder why the difference :confused:

[bwanajim]

Here's what I do in all 4 of my Pikes on 72mHz:

1) Double the antenna length
2) Run the antenna down the fuse inside a long shrink wrap tube (I don't shrink the tube)
3) Exit the antenna forward of the fin post through a rubber grommet. You should have some 18"+ dangling off the tail.

Works every time. Range checks to 60+ paces. I use JR R770 and R649 RX exclusively in all my TD planes.

--Jim

[Mark Miller]

In my Evolution XL which is similar construction to the Pike I have the antenna inside the fuselage and exit behind the wing. it is routes up to the top of the fin. I added length to the antenna to give a full 40" outside the fuselage. I hate the way it looks but don't want to have problems. You can do range tests on the ground but many times you are further away in the air and can't do anything about loosing signal.

Mark Miller

[yardflier]

[QUOTE=jojoen]Today I flew a Supra glassfiber and had the antenna in the midsection. From the 9 pin plug I had two ends. One to the end of the midsection and one to the servo bay. The Rx was a JR770 on 72mhz and was placed under the servos. Did not do any ground tests but was probably 7-800m out (2300-2600ft). The Rx was set to go full crow if I was too far. Never experienced anything. While I was out there I both had the Tx on the ground and pointing different ways. Again no problem.
[QUOTE]

JoJo,

You may be going thru a lot more trouble than you need to. I have the same exact Supra (down to the color) and fly it with the exact radio gear you are using( JR 770 on 72 mhz and 9303 transmitter).

My antenna is 100% inside the carbon boom and my range check is excellent. I regularly fly this plane to the edge of my vision range with no indication of trouble whatsoever.

Luis

[jojoen]

With a good receiver this is not needed and will both disturb your rudder and is ugly as you say...

[carrinsr]

I angle drill a small pilot hole (not quite as big as a round toothpick) in the bottom of the fuselage, at least two inches behind the tow hook, and then use electrical tape to secure the antenna wire along the bottom of the fuse and tail boom. I've done it this way on every sailplane I fly and I've never had one problem. Not one. And I like to spec out my Super Ava and Sailaire, and keep them up until I become concerned about batteries. Works for me!

David

[Mark Miller]

I find this all confusing. Depending to who you get information from, things are different. Everyone is sure their method is the only way that works. Some like it all inside the fuse, some like a bit out the back, some like it up to the fin. I'm going to have little holes drilled all over this thing and still fear I'm wrong.

Mark Miller

[jojoen]

I find this all confusing. Depending to who you get information from, things are different. Everyone is sure their method is the only way that works. Some like it all inside the fuse, some like a bit out the back, some like it up to the fin. I'm going to have little holes drilled all over this thing and still fear I'm wrong.

Mark Miller
Why?
There are many solutions to a problem. As many have stated the point is to test untill you get a sufficient range.

[scalebldr]

Just finished my PIKE Sup Installed the new JR syn 790 7 ch reciver, with a new JR 9303 raido with a Syn tx mod on ch 42. Ant is all inside, will let you know of my range testing. Hope this works. Talked with Skip M. he uses all Airtronics with no problems with inside ant.

[scalebldr]

Ok, did range test with ant. inside with raido ant down and we got 180 feet before the wearding way statred. Next pulled ant out of fuse got another 50 feet, or 230 feet. Next changed to standard spcm 7 ch 770 rx and got same results. Am I confused or what, can any body tell me, is 180 feet OK?
or mabe I should order a fuse from samba that has a Kevlar boom and carbon in the nose only?