UHF Aerials info

Submitted: Wednesday, Nov 05, 2014 at 01:20
ThreadID: 110043 Views:1732 Replies:5 FollowUps:4
This Thread has been Archived
I have a GME 4018K aerial which has snapped off at the bottom of the black covering. It has done 190,000 k's on many rough roads so I am not really surprised that it has broken. I brought a non genuine replacement at Mobile Masters in Perth for $39. The bloke that served me was a mind of information which I did not know so I though I would share what I learnt. Non mental aerials are recommended for diesel vehicles as the vibration of a diesel engine adds to metal fatigue. The GME 4018K aerial come in two parts, the base which includes the spring which is metal, and the screw on top which is fibreglass. The top gives about 4.5dB gain and the base gives about 2dB gain giving a total of 6.5dB gain. He highly recommends this type of aerial for vehicles that cover a variety of terrains, that a general purpose. If your aerial breaks you may still get some incoming. However if you transmit with a broken aerial you are like to cause damage to the transmitter in your radio. This damage is usually repairable but you would have to take the radio out of your vehicle to get it fixed. He strongly recommends that should your aerial break that you turn off your radio immediately. I now carry a spare just in case, little weight and easy to poke in somewhere. I will take some photo's tomorrow.
What other people think of me is none of my business.
Do unto others what you would have them do unto you.

Lifetime Member
My Profile  My Blog  My Position  Send Message

Back Expand Un-Read 0 Moderator

Reply By: Idler Chris - Wednesday, Nov 05, 2014 at 01:23

Wednesday, Nov 05, 2014 at 01:23
If anyone is wondering why I would be posting at 1:20am well I am not. I am currently in Perth which is 3 hours behind.
What other people think of me is none of my business.
Do unto others what you would have them do unto you.

Lifetime Member
My Profile  My Blog  My Position  Send Message

AnswerID: 541310

Follow Up By: Zebra400 - Wednesday, Nov 05, 2014 at 05:31

Wednesday, Nov 05, 2014 at 05:31
Thanks for the update Chris. I wondered where you are. Has your SPOT broken as well, as it says you haven't moved for one month. It looks like you are stuck in a house in Fremantle atm.
0
FollowupID: 827405

Reply By: Kris and Kev - Wednesday, Nov 05, 2014 at 07:27

Wednesday, Nov 05, 2014 at 07:27
And when the top breaks off it can do this... The breakage was caused by a bird strike... The bottom of the broken antenna hit the screen. The bird was OK, not our windscreen.. Kevin


AnswerID: 541315

Reply By: Member - cherrywipe - Wednesday, Nov 05, 2014 at 07:39

Wednesday, Nov 05, 2014 at 07:39
Hi Chis,
Sound like the aerial had a MENTAL breakdown. lol.
Cheers Cherry.
AnswerID: 541317

Reply By: Robin Miller - Wednesday, Nov 05, 2014 at 08:14

Wednesday, Nov 05, 2014 at 08:14
Hi Chris

I have seen to many of those type break and is why I always recomend the little 1/4 wave in middle of roof for those who can do it , it works better in almost every respect.

Glad you got yours fixed ok and hope it lasts another 190,000km.

I wouldn't worry to much about turning your radio off if you lose an aerial, behind what he is saying is that a high VSWR can cause a wrong load to be placed of the output of the radio , however these days almost all radios have a shutdown mode for the transmitter when an abnormal load is sensed.

On out latest trip Muz's antenna like that developed a fault an I got a small piece of solid wire and just stuck it in place with some masking tape and this worked until we got to repair it properly.
Robin Miller

Member
My Profile  Send Message

AnswerID: 541318

Follow Up By: HKB Electronics - Wednesday, Nov 05, 2014 at 09:21

Wednesday, Nov 05, 2014 at 09:21
One would expect that in this day and age "all" transceivers would have output protection, but it seems at least one very popular UHF radio is very susceptible to damage in this regard, so much so I seems to recall reading that the output module is a plug in unit!

Lifetime Member
My Profile  Send Message

0
FollowupID: 827413

Follow Up By: Robin Miller - Wednesday, Nov 05, 2014 at 09:55

Wednesday, Nov 05, 2014 at 09:55
Lets us know who if you can HKB (just first letter of name should do.

Its strange how these things go , when I designed UHF amps which usually used plug in linear modules , we always tried to use SMD as far as possible as the cost of pins into which a module would be plugged made it uneconomic (along with reduced reliability).
Then the move was made by some e.g. Uniden into mounting the module against the case for heatsinking - which worked but then lead to signifcant fatigue failures where the connections were soldered to the board.

All this lead to better and inbuilt protection for both heat and voltages spikes , i.e. shutdown was cheaper than better fundamental design , but hey thats our world today !
Robin Miller

Member
My Profile  Send Message

0
FollowupID: 827417

Follow Up By: Peter_n_Margaret - Wednesday, Nov 05, 2014 at 15:08

Wednesday, Nov 05, 2014 at 15:08
"....I always recomend the little 1/4 wave in middle of roof for those who can do it , it works better in almost every respect."
Yep....
Cheap, clear. almost indestructible.....



Cheers,
Peter
OKA19 Motorhome
0
FollowupID: 827430

Reply By: Nomadic Navara - Wednesday, Nov 05, 2014 at 16:51

Wednesday, Nov 05, 2014 at 16:51
The transmitters of the first generation two way radios certainly self destructed when the antenna was removed of fiddled with. However I have not seen this happen since the very early 1970s. Your mate certainly is not in tune with modern radios.

Hid knowledge of antennas is lacking. The silver sleeve on the base unit of one of those antennas is actually half of a half wave dipole. A dipole has a gain of 2.2 dBi when it is entire. If you loose half the antenna its gain will be far less than 2.2 dBi (probably well into the negative region.) My guess is you will probably picking up more signal through the poor shielding of the cheap (and single shielded) co-axial cable than you are getting from the screw thread on top of the antenna.


PeterD
Retired radio and electronics technician

Lifetime Member
My Profile  Send Message

AnswerID: 541335

Sponsored Links

Popular Products (13)