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K40 base load vs. Firestick top load

tuner

tuner

Active Member
Jul 25, 2010
229
41
38
Canada
Hi Guys,

Just looking for info in regards to the k40 antenna trunk lip mount.
In comparison to a 5' fiberglass Firestick top loaded on a trunk lip mount.

I only run about 200 watts. I read that a top loaded antenna and a center loaded antenna is more efficient than a base loaded antenna.

Any thoughts , comments would be greatly appreciated (y)

Thanks ,Tuner
 

tuner said:
Hi Guys,

Just looking for info in regards to the k40 antenna trunk lip mount.
In comparison to a 5' fiberglass Firestick top loaded on a trunk lip mount.

I only run about 200 watts. I read that a top loaded antenna and a center loaded antenna is more efficient than a base loaded antenna.

Any thoughts , comments would be greatly appreciated (y)

Thanks ,Tuner
Click to expand...

I have the K40 trunk lip mount. I've been a bit disappointed in the SWR I get with it. 1.8 is as low as I can get it. I've had a couple before and was able to get it much lower.....like 1.1 - 1.2 range. It might have more to do with the vehicle it is on.
 
tuner said:
Hi Guys,

Just looking for info in regards to the k40 antenna trunk lip mount.
In comparison to a 5' fiberglass Firestick top loaded on a trunk lip mount.

I only run about 200 watts. I read that a top loaded antenna and a center loaded antenna is more efficient than a base loaded antenna.

Any thoughts , comments would be greatly appreciated (y)

Thanks ,Tuner
Click to expand...

I run about 200 watts, I tried my K40 on the trunk lid of my car and my SWR was high, almost 3. I used the magnet mount K40 on the rear of the roof and now SWR is almost flat across the band. Unless you mount it on the lip of a hatchback or a liftgate on a truck you might be ok. You want the coil above the roof line for best performance.

Also the trunk lid mount would gradually come loose and then the "lip" on the K40 lip mount would start to stretch apart as I would tighten the screws to secure it to the trunk lid.

.02
 
k40 magnet mounted works wonders for my work truck . work the whole country no problems . swr is just fine . great antenna
 
tuner said:
I read that a top loaded antenna and a center loaded antenna is more efficient than a base loaded antenna.
Click to expand...

What you read is true, but that doesn't mean that you will actually notice any difference...

There are also other tradeoffs of putting the coil further up the antenna. For example, the coil is a current device, so moving it away from the current node, which is at the base of a mobile antenna, means it will have less of a shortening effect on the antenna as a whole. To compensate you must make it larger, which will again lower the coil's efficiency.

In the end it all balances out.


The DB
 
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Instead of a K40,get a Sirio Performer PL5000. Also get the Sirio mag mount if you don't like drilling holes in your auto.
I've had the K40 and magmount. The Sirio does so much better than the K40 and vswr issues are a nonissue for the 5000 in my case plus the 5000 has rubber seals on it as well as a stick on bottom skin cover to keep moisture out. The K40 is prone to vswr problems especially with wind driven rain and car washes.
Sirio Performer 5000 PL 10m & CB Mobile Antenna [p5k] - $68.00 : Sirio Antenna, High Performance Antenna Made in Italy

Sirio Mag 145 PL Magnetic Mount and Cable [mag145pl] - $34.50 : Sirio Antenna, High Performance Antenna Made in Italy

http://www.sirioantenna.com/index.php?main_page=product_info&cPath=2_65&products_id=252


Mounts: http://www.sirioantenna.com/index.php?main_page=index&cPath=2_65
 
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Firstly the Firestik isn't top loaded, its continuously loaded all the way up the antenna, the majority being at the tip, only decent one was the original 7ft version.

Secondly the K40 is an over priced, over rated antenna with a very narrow bandwidth.

You'd be much better with a Sirio Hp4000,Megawatt 4000 or Performer 5000, all great antennas and pretty much standard with dx'ers across Europe and now people in the states are realising they blow away everything there except a body mounted fullsize 108" whip trimmed for best swr, In Europe I've been using Sirio HP4000's/Megawatt 4000's for 15 years, won't use anything else because nothing else touches it that can be used mobile except the other sirios, a fullsize whip ain't practical mobile but is ok for static mobile, the mag 145pl is the base to go for for it, with proper mil spec RG58C/U or use a sirio SO239/DV body mounted base which is even better if mounted dead centre of roof where magmount should also go too.

Any other mounting position is a compromise, all antennas should be mounted at heighest most central point of vehicle for best performance, there is no magic antenna design to get round that. You just can't go wrong with sirios up to about 250w unless you use a fullsize 1/4 wave whip.
 
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tuner said:
Thanks Jazz


Sent from my iPhone using Tapatalk
Click to expand...

NP mate, better to buy the best from the start which saves you having to ugrade later, if it costs you a 100 dollars or so and you look at it as 2 dollars a week to have a good signal, then every week it lasts after that are free, that's how I look at it, just bought another hy power 4000 mag145pl myself for 57 pounds delivered here, a pound a week for a year its paid for, bases are easy to rewire if you jam coax, I've had 4 Hp4000's and 2 Megawatt 4000 along with a hp3000 over the past 15 years, I keep selling them for one reason or another and rebuying them, Only 2 other antennas I'd consider outwith the performer 5000 is a full 108" 1/4 wave whip or a very cheap but very effective UK antenna called the Modulator or any of its many clones, they do exceptionally well and are a handy backup, sirio also does a SO239/3/8 adapter that can allow the mag145pl to take 3/8 threaded antennas too and even a 3/8 to dv27 adaptor which goes on top which basically allows you to mount 99.99% of mobile cb or ham antennas to that mount, very versatile, I've seen avanti moonraker av261 mag bases come off a few times, but never seen a Sirio come off, even with the 6ft 7" whip on hp4000, add a small linear RM KL203p or similar or use a ic706 or TS50 and you'll work the world on the Sirios, easily.

I feel bare without one and always end up buying new ones, they do what they say on the tin, just don't take power handling or quoted gain figures seriously but trust me they work very very well and a £ or $2 dollars a week is a very small price to pay for an antenna that will mesmerise you on mobile signal reports, get it up high on a hill or mountain and it will bang out. :)
 
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Thanks very much Jazz, I was hoping to get a trunk lip mount but I guess the mag will be fine. I know it works better on the roof but I just don't like the look of it on my car lol. I'm looking around to see what US dealers will ship to Canada.


Sent from my iPhone using Tapatalk
 
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Just as a side note, the K-40 uses a small ceramic disk cap located right across the coax inside the mount. It's almost certain this small cap was chosen to limit maximum power since every aspect of the K-40 was robust enough to handle power except this hidden cap. If you notice your K-40 refuses to tune properly this cap has probably blown.
 

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