Bill, FWIW, I'm using 30 turns of 9913 coax close wound on a length of 8" ID PVC tube. Works very well for me.
Jim / W6JHB On Wednesday, Oct 2, 2013, at Wednesday, 10:04 AM, Bill Stewart wrote: > 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 _________________ Topband Reflector
