The QRPGuys Multi-Band End Fed Antenna is designed as a portable 40/30/20m two trap wire antenna with a built-in tuner and SWR indicator. It consists of a main board with tuner and SWR indicator, two trap pcb’s and an end wire support. It incorporates the N7VE led SWR indicator and has a board mounted female BNC for connection to your rig. The built-in absorption bridge design will ensure you do not damage your finals with a poor SWR. Our test show and SWR of 1:1 on 20m, 1.1:1 on 30m, and 1.3:1 or better on 40m. It is rated for 5 watts continuous, 10 watts PEP. The kit comes complete except for the user supplied #22-24awg wire for the elements. All S.S. connection hardware for the radiator and counterpoise connections. The tools required are a soldering iron with a small tip, rosin core solder, small side cutters, and can be built in an hour or two. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 2.
N.B. - I am not affiliated with any company that you see that has products that appear in this blog. I deem these posts to be newsworthy enough to share with the greater QRP community.
72 de Larry W2LJ
QRP - When you care to send the very least!
If you have a tuner, what do you need the traps for??
ReplyDeleteIf you want the maximum in qrp pse forget traps and tuners 73
ReplyDeleteThe traps are there for people who have rigs that do not have built in tuners; or do not want to carry an external tuner.
ReplyDeleteYes, traps and tuners do incur a small loss; but if you're operating portable and want to communicate on more than one band; do you want to spend your operating time on the air - or putting up resonant antennas for each band?
ReplyDeleteIs convinient using an unun with 2 radiators attached to it, lets say one for 30m and other for 17 and the rf will find its route with ease
ReplyDeleteAnonymous wrote: "Is convinient using an unun with 2 radiators attached to it, lets say one for 30m and other for 17 and the rf will find its route with ease"
DeleteNo, it won't. I assume your Unun is designed to feed into a high impedance antenna such as an EFHW. The 17 m antenna will be a bit longer than a quarter wave long on 30 m and would present an impedance Z = R + jX, where R is somewhat higher than 50 ohms and X might be several hundred ohms, on that band. This would be placed in parallel with the several thousand ohm resistive impedance of the 30 ohm EFHW antenna on that band. How well do you think that is going to work on 30 m, when tied to the high impedance end of the Unun?
It's just as bad on 17 m. Here the 30 m antenna is going to be a bit shorter than a full wave long on 17 m and will present a fairly high resistance in parallel with some inductance, on that band. Putting that in parallel with the high resistive impedance of the 17 m EFHW antenna will reduce the resistance a lot below what the Unun wants to see, plus put that inductive reactance in parallel with it.
I'd far rather use traps and avoid all this, or use a tuner with a single wire a half wave long on the lowest frequency band, or use links on insulators to make the thing a half wave long on whatever band I was using.
Paralleling antennas works not too badly with low-impedance center-fed dipoles, though the interaction and resulting necessary trimming is more than I like. Paralleling high impedance antennas is as you can see a different story.
Knowing just a little bit about how Z = R + jX and Y = G + jB work (this takes 11th or 12th grade algebra) helps one avoid such mistakes.
David VE7EZM and AF7BZ
VE7EZM thanks for infos (I'm not so good in algebra) 73
ReplyDelete