two antennas on one receiver?

[andi]

Hello gents,

having troubles sometimes with those micro receivers, resulting
in motor cutoffs for the split of a second (sometimes longer) I
wonder wether it makes sense to add a second antenna onto the receiver? The problem appears only when the airplane is
heading straight towards me and the the tx antenna is pointed
straight to the aircraft , giving the weakest field strength possible. Several test flights let me exclude all other reasons
(battery, ESC,...) and the problem can be solved every time by
turning the tx to make it a right angle to the model. So what do
you think about two receiver antennas, one along the fuselage
(as it is now) and the second running to the wingtip?


Thanks for any inputs

Andi

[Dave Robelen]

Hello Andi,
This is the first time I have heard this mentioned with the micro receivers (you did not mention brand). I have had fine results with the GWS, SHR, and RFFS-100. One option that worked years ago was to install a length of wire in the wing and attach the center of it to the receiver input. The total length should not be longer than the original single wire.
Regards, Dave

[Dr Kiwi]

Dear Andi and Dave,
Your "conversation" has spurred me into asking a question! I am interested in building several sea planes because (a) I live alongside the Tennessee River and therefore we have lots of dam lakes nearby and (b) I spend summers on an island in Maine with my family and the cove below our cottage would provide an ideal site for flying seaplanes (I know that electricity and salt water don't mix well [I own a Boston Whaler so I know!] but I'm hoping it's worth the risk!). Among the plans I have on hand are Pond Baby (for Wes Tech Micro 5-2.4) and Watter (for Speed 480). I also have a kit for Donald 4 (on which I want to try my Phasor 15/4, since it seems to me and Moto Calc that a plain 600 is not going to get it off the water!). My question (after this verbose preamble) concerns the most suitable type of receiver antenna, which one obviously does not want to leave trailing in the water. The standard solution seems to be a car-type whip antenna. I have just purchased a Deans Mini Antenna P.N. 1102 and have read about something called an EEN antenna used on a reviewed model of the Radical R/C Edge 540. [What the h..... is an EEN antenna and where does one get one?] I wonder if you knowledgeable gentlemen could give me the pros and cons of whip aerials, versus (a) Dave's idea of a wire within the wing, connected at the midpoint to the receiver or (b) stringing the standard receiver wire, say, around the periphery of the wing or perhaps back and forth along the main spar, so that it could not trail in the water. Any assistance greatly appreciated. Cheers, Phil (a.k.a. "Dr Kiwi")

[Dave Robelen]

Hello "Dr Kiwi",
Actually, I had forgotten the success I had with a whip antenna on the seaplane. I have done several, and the whip has worked fine for me. I should have mentioned that as a solution to the "blind spots". As far as the Deans or Azarr antennas I have no personal experience, but there certainly is a lot of positive comment about the "shorties". Coming from the sone age as I am, I would lean toward a whip antenne with a length that matches the original equipment.
Regards, dave

[andi]

Hello Dr Kiwi, hello Dave,

yes, the whip antenna provides the best receiving. However I
would not shorten it. That leads to the problem that it creates
a lot of drag and therefore I don´t use it- even trailing the antenna on my Dumas Mr. Mulligan made it turn in one direction.

I don´t know what an EEN antenna is.
Dave, the receiver I use is a multiplex pico 3/4 indoor.
For scale appearance I want to hide the antenna inside, but, Kiwi,
do not lay it in circles back and forth , it has to be straight to do its job. I will try to extend the length, what I have learned in the meantime is that this is possible as long as you make changes in
whole numbers e.g. original length times 2, times 4 and so on.
So I am thinking of a solution where the original one goes along
the fuselage and a second one, with the same length, as Dave
described in his post . So there should always be some "light"
in the cable!

[Dr Kiwi]

Originally posted by Dave Robelen
Hello "Dr Kiwi",
Actually, I had forgotten the success I had with a whip antenna on the seaplane. I have done several, and the whip has worked fine for me. I should have mentioned that as a solution to the "blind spots". As far as the Deans or Azarr antennas I have no personal experience, but there certainly is a lot of positive comment about the "shorties". Coming from the sone age as I am, I would lean toward a whip antenne with a length that matches the original equipment.
Regards, dave

Dear Dave, This Deans mini antenna has a short, white, flexible, external "whip" section which is 7" long. Attached to its base there is 8" of what appears to be standard antenna wire, with a tiny female connector at the free end. It is suggested that one cut all but 4"-10" from one's standard receiver antenna, attach to it the supplied male connector and then join it to the 8" wire from the whip aerial's base. This would give a total length of 19"-25", as a replacement for the original 36" of the Hitec Feather I'm using. I can only assume that the whip part of the Deans is capable of compensating for this reduction in overall length. The wording on the package only exacerbates my dilemma, since it states "Use with a 36"-39" antenna" - I can only surmise that it was meant to read "Use in place of a 36"-39" antenna. What do you gurus, collectively, think about this. I suppose Deans has a website - perhaps I should ask them what the deal is! Cheers, Phil

[Dave Robelen]

Hello Dr. Kiwi,
Regarding the shortened and "loaded" antennas, it has been my impression that some range would be lost compared to the original based on the intended applications. These antenna designs were originally marketed for helicopters and similar vehicles that were using a "full performance" receiver and could tolerate the reduction in absolute range. In the early days of R/C (circa 1953) we found that the whip installation had the best performance with marginal receivers. It was also fairly common to find modelers installing a foil 'ground plane" in the model which was attached to the receiver ground. Times have changed eh?
Cheers, Dave

[Taylorcraft]

Indeed times have changed!

Today a receiver antenna should NOT be shortened, unless you attach it to a loaded whip. These whips oughta come with instructions on how much to cut the original antenna, follow them carefully!

Like said before, it should run as straight as possible, or in a 90 deg. angle, however this CAN lead to a weaker signal. Under NO circumstances should the antenna be folded or rolled up, this is asking for disaster...

Basically, an antenna folded in half produces no signal. When folded at 75% of the length, only the inner 50% is picking up the signal.

Two antennas connected to a receiver is bad medicine as well. They will confuse eachother, and, in worst case they will take eachother out, causing a big fat zero in signal strength on the receiver -> crash.

Suggestion:
Plan ahead. Run the antenna away from batteries, ESCs, servos and other cables, as straight as possible (or in the previous mentioned 90 deg. angle). In some cases you MAY get away with rolling the antenna around a tube, with about a centimeter between the coils, to make it shorter, but basically this is "not supported"... :)

ALWAYS perform a radio range check before flying!

And, the radio check should preferably be done from several angles with the transmitter antenna fully retracted.

BRG

Taylorcraft