Tnx Richard for the info. I've got a small collection of doorknobs and will ck to see if I can cobble up that much capacitance. I only run less than 200 watts output, so won't need any HV vacuum caps. From what I read, the inv L can be fed directly with 50 ohm coax, but no mention is made of what the swr might be. In an open field, made per the book, the swr might be much lower than mine. My ant. has a lot of tall pines close to it.
I thought the "Q" of the antenna was not vry good since the SWR curve is vry broad. The choke you mention..is it made with coax coiled up at the feed point..if so, any idea how many turns & coil dia? Last night I made contacts into Minn, NY and PA, with 589 reports.. running a Viking 2 at 100w output. Oh, and receiving seems to be good too...W1AW overloaded my SX-71 and other stns were cmg in good as well...so some success. Tnx, 73 de Bill K4JYS ----- Original Message ----- From: "Richard Karlquist" <[email protected]> To: [email protected] Sent: Tuesday, October 1, 2013 6:14:12 PM Subject: Re: Topband: 160m Inverted L High SWR On 2013-10-01 14:08, Bill Stewart wrote: > Good afternoon all, > The vert. section is > abt 55 ft & the rest is nearly flat horizontal. Total length is 130 > ft/6 in. I am using a > 4 wire c-poise abt 9 ft high of which none are directly under the > horiz. section. > Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz. > The SWR This is exactly what you would expect. It corresponds to a drive impedance of something like 18 ohms, about right for a top loaded 55 foot vertical. You will need to put a shunt capacitor of about 2400 pF across your coax, and then increase the length of the L until you get the resonance to 1833 kHz. I currently have a top loaded 60 foot vertical and this is very similar to my situation. You will find that after proper matching, the bandwidth is really quite narrow, indicating reasonable efficiency. You should probably add a common mode choke at the feedpoint if you don't already have one. Rick N6RK _________________ Topband Reflector _________________ Topband Reflector
