Weird SWR Readings from a 3ft Firestik on a mag-mount

Hi all, well been testing my brand new Firestik, and its tuned to 10M? SWR Readings below:

28.315 = 1:1.6
28.755 = 1:1.2

27.415 = 1:6.1
27.635 = 1:4.8

27.78125 = 1:4.4

This boasts a couple of issues, firstly its nearly resonant at 28.7, but if my calcs are correct , the antenna is too short on 27Mhz, so how do you make a Firestik longer?? Bear with me if Ive got it totally wrong as I'm confused why a CB antenna is tuned to perfect on 10M ??

Thanks for listening to my drivel, cheers Tony

Hi Tony,

The range of 'Firestik' antennas can be problematical especially regarding grounding and is one of the reasons they offer two main versions to include the NGP range. (No Ground Plane).

They're a weird design in helically coiling up a 5/8ths wave electrical length of wire on a fibreglass rod but some people swear by them. Back in the day you simply drilled a big old hole in the metal chassis of your car and bolted it on ensuring a good ground plane. Most don't want to be drilling holes in their modern cars nowadays!!!

If it helps any the 'Firestik' company do have a technical support section on their site as follows :-

http://www.firestik.com/Tech_Docs.him


I've personally never really rated the Firestik antennas highly, a three foot fibreglass stick coiled with wire is hardly a great design and you'd be lucky to make it across a car park to another CB user. Joking aside they are a bit of a compromise like a 'rubber duck' on a handheld.

Sorry if that's not great news, but there are far better/less problematical antennas out there. We live and learn.  


All the best,
Victor

Hi Victor,

Thanks for your reply , I agree totally in what you say, Back in the day I had 2 x 6 foot Firestiks on my HGV wing mirrors (Co-Phased), back then any antenna worked , not today sadly. Ive decided to put the ML145 on my car from now, and have just ordered a Sirio GainMaster for Home QTH, so onwards and upwards , Fingers Crossed eh? cheers

How is it mounted?  Just about every tuning problem I have seen with a Firestik is insufficient groundplane.

Also, what model did you get?  (Just checking you didn't get the NGP one Victor mentioned, as these are meant to go with a matching section of tuned coax they also sell which acts as a counterpoise).

43CT016 wrote:

How is it mounted?  Just about every tuning problem I have seen with a Firestik is insufficient groundplane.

Also, what model did you get?  (Just checking you didn't get the NGP one Victor mentioned, as these are meant to go with a matching section of tuned coax they also sell which acts as a counterpoise).

Hi Jeff, It's Mounted on a 7 inch Magmount in the centre of the roof of my all metal car, the weird bit is it's spot on SWR on 10m, so to me it's got enough GP but possibly not enough wound wire? 

Its a standard 3ft Stik, our local truck stop only supplies standard ones. I have also measured the coax and its a 1/2 wave on 11m at 5.5m long from PL to mag connection? cheers

Okay it seems I have made another "Schoolboy Error" , Because it's been such a long while since on 11m, I have forgotten all the basics. Thanks to Victor for the link to Firestik Tech Team.  

I measured the length of the Loaded section to confirm non NGP, so all good there, it was then I remembered there is a tuning stub at the top of Firestiks to allow altering of the resonance. 

so I answered my own question of how do I make a Firestik longer. anyway armed with all the correct info I will try to adjust it get it close to resonant at 27.555 before I return it.

BAREFOOT wrote:

Its a standard 3ft Stik,

Not even going to bother to give any suggestions other than to replace with a decent antenna. The performance of a 3ft antenna is absolutely dire. They'll get 2-3 miles on a good day and are only really of any use as a standby antenna to use on a hire car when you're on a road trip with friends in other cars and want some form of comms between the vehicles.

For a vehicle of my own I wouldn't entertain a 3ft antenna. I also would never ever entertain something that didn't bend because inevitably you're going to forget its on as you go under a low height barrier or you're going to come across a low hanging branch you weren't expecting. In either case with an antenna like a Firestik you're going to be bending the metal of the car if you're using a fixed or lip mount or the magmount is going to be pulled off the vehicle and then it's on a magical mystery tour where the possibilities are it putting a dint in your car or going through a window.