Aerial positioning

[geconParticipant @gecon]

Hi, is positioning of the receiver aerial for modern 2,4ghz R/C critical?

Can the aeriel be left inside the hull of a yacht?

Or does it need to be routed out of the hull ASAP and away from motor/wiring etc?

The aerial I have is only 145mm long and the instructions say the last 5cm is the 'active' part. It cannot be routed very far away from anything -it's so short.

George

Edited By George Edward Connery on 02/06/2020 22:18:22

[geconParticipant @gecon]

Any opinions?

[Colin BishopModerator @colinbishop34627]

The important thing is to ensure it is above the waterline. Even better if you can get the last bit above deck, perhaps in a short vertical plastic tube below the boom.

Colin

[Tim RoweParticipant @timrowe83142]

HI George

The aerial can stay inside the boat unless it is metal hulled or carbon. It is only the last bit that is "active" as supped to the "old" aerials where the whole length was part of the tuning.

I think getting the aerial as high as possible in the hull is good and as far away as possible from motors, ESCs batteries as possible given the limitations and again above them if possible. 1.4gig does not have the penetrating power as the 40meg sets so driving a model behind a large boat runs the risk of losing contact so I avoid ding that.

Much simpler really.

Tim R

PS Colin types faster.  Some receivers have a short aerial and a longer one like you have.  These should be orientated at 90 degrees to each other but it doesn't matter in which plane.  In these cases I use the plastic tube method to keep them correctly orientated.

Edited By Tim Rowe on 02/06/2020 22:31:06

Edited By Tim Rowe on 02/06/2020 22:31:55

[geconParticipant @gecon]

Thanks gentlemen,

I have now 'Velcro-ed' the Rx to the underside of the starboard hatch frame and routed the aerial aft and throught the cockpit bulkhead and out into the open cockpit area. A short length of plastic tube keeps it straight -and protected.

For the time being it's more or less parallel to the water line. I'll do a range test with motor running within a few days and if necessary I can try moving the Rx further aft so the aerial can be vertical-ish without being able to snag the sheet to the main boom. Normally this sheet is relatively taught but if slack, it could snag on a vertical aerial and in time cause fatigue due to constant movement about the exit point from the hull.

The morning coffee is kicking in now and having 'absorbed' your inputs even further, I will probably re-locate the Rx as far aft as possible under the hatch opening and try to get the aerial more vertical. Photos will be posted in Album.

Again, many thanks for your responses,

George

[ashley needhamParticipant @ashleyneedham69188]

George. Unless you are boating at a considerable distance, simply having the aerial as Colin says above water will be fine. Mine work fine in the lander, where everything is bunched in tight.

All mine are "below decks" as it were and I have never bothered to try and get them side-side or fore-aft etc.

Ashley

[geconParticipant @gecon]

Thanks Ashley, suits me well to have it below deck/above w/l. I'll try that for the first range test. Not planning for longrange yachting. After so much effort I want be able to SEE it😀

George

[Tim CooperParticipant @timcooper90034]

George

All mine are inside the hull with no problems. Just be careful with the active part of the aerial. On my Italeri S100 I managed to trap the aerial at some point and lose most of the active part. Range on that Rx is now about 50 to 60 feet or 15 to 18 metres.

Tim

[geconParticipant @gecon]

Hi Tim,

many thanks for the info'. 'White wine with the fish' this evening, so doing the aerial tomorrow! Removing the previously installed tube and taking the internal option.

George

[Malcolm FraryParticipant @malcolmfrary95515]

The shiny bit at the end is a tuned length, shortening it will reduce its ability to receive signal.

It is a small coax cable, the shiny bit is just where the outer sleeve and the layer of wire that forms the shield removed, leaving the inner wire inside its insulation. Restoring the original length of stripped outer should restore most of the original range. Most, because the length of the shield is also a tuned length. Its almost 60 years since I had to do the theory about such things for an exam, and its been gathering dust ever since I handed the paper in.

[Dave MilbournParticipant @davemilbourn48782]

Malcolm

Did they actually have microwave frequencies back then? I thought it was mostly cat's whiskers and valves, and aerials were about thirty feet tall and put up without planning permission by spotty geeks in garden sheds…

DM (I remember Hilversum on the dial, too)

[Colin BishopModerator @colinbishop34627]

And Radio Luxembourg…

Ah the smell of those old valve radios with their illuminated dials… Pure nostalgia.

And the live chassis as I inadvertently discovered.

Colin

[geconParticipant @gecon]

Interesting to see how a thread develops, digresses and diverges as nostalgia 'kicks in'!

Posting some pics in album of the aerial route-change later today. Hope it's not going to be below the W/L when the yacht is sailing. If so, I'll route the aerial up through the cockpit combing. Launch day/sea trials should be possible when the rain stops…after the weekend.

Thanks to all,

George

Edited By George Edward Connery on 04/06/2020 08:53:33

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by Dave Milbourn on 03/06/2020 18:02:15:

Malcolm

Did they actually have microwave frequencies back then? I thought it was mostly cat's whiskers and valves, and aerials were about thirty feet tall and put up without planning permission by spotty geeks in garden sheds…

DM (I remember Hilversum on the dial, too)

We got taught about all sorts of stuff that I never went near after handing the exam paper in. First year CGLI insisted that we know about magneto exchanges, of which there was a total of one left in the country. Later years they got quite forward looking, especially the theory bit where actual experience on the part of the syllabus writers was not needed. I wandered away from Radio and Line Transmission and into the Telephony side of things, so the oddments of what happens to high frequency electric going up cabes sort of faded. I remember "Droitwitch" on the dial. Much more evocative than a row of numbers.

Returning to original question and the last post – if the end bit of the antenna is taped to the underside of the deck near to the center line, or pushed into a plastic tube taped there, it should never be below water unless something terrible has happened, when I suspect that a loss of signal is the least of your problems.

[ashley needhamParticipant @ashleyneedham69188]

Cor. radio and line transmission! Takes me back. Impedance matching, building-out networks, line repeaters.

Did nothing earlier than Strowger telephony when I joined the GPO.

Learned all about aerials not that I used any of it.

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

Very very shortly after my 1st year Penwortham exchange went auto. So there was nobody left in the country who had to "ring off" at the end of their call, although the phrase persisted. I never had cause to go there, it was the wrong side of the river.

Like yourself, I never used any of that area of theory, but I did have an older workmate who had done National Service as a radar tech, and had formulae dripping out of his earhole when he canted his head. He used to have meaningful discussions with the local CAA radar satation when he was sorting out interference on his video recorder. It seems that it broadcast on the default UHF channel that video recorders output on.

The trick on models using 2G4 is to just have the shiny bit as hgh and straight as possible to collect the maximum signal. Messing with a critical length of coax shielding does run the risk of an impedance missmatch, but it is very possible that any extra loss would only be noticed using the right test gear.

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