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Hello Peter,
<p style=”text-align: left;”>It is ok to keep it connected. I leave mine on the SWR scale. That way I constantly know if my SWR is low and ok.</p>
If I’ve selected the wrong antenna, a falling branch has damaged my antenna, or a animal has damaged my coax I will quickly notice the high SWR, hopefully before I damage my radio.The one time it is good to leave the feed line free of extra accessories is when operating QRP where every watt of power to the antenna needed.
Hamilton K1HMS
Hello Russ,
There are no issues with running both feed lines down the mast.
The antennas have negligible coupling to the feed lines.
The fan dipole needs a balun so its feed line isn’t part of the antenna. I’m assuming the U/V antenna has a ground plane
73
Hamilton K1HMS
Hello Bob,
Congrats on the licenses.
The height above the ground of an HF dipole (straight wire, inverted V, Yagi) determines its pattern.
At 1/2 wave high it will have a fairly low elevation angle and a directional figure 8 azimuth pattern making it good for DX but poor for local and regional QSOs.
As the height is reduced to 1/4 wave and below the main beam of a dipole will be nearly straight up and the azimuth pattern will be omnidirectional. Since it is omnidirectional (non-directional) the orientation is not a factor. This is good for local and regional QSOs, but poor for DX.
1/2 wave on 40m is 66′ but on 20m it is only 33′.
Propagation isn’t completely predictable, occasionally you can have a DX QSO with a low antenna or work the next state with a higher antenna. I have a 40m wire antenna at over 1/2 wave high and can rarely hear a local net control or log an adjacent state during 13 Colonies or the NE QSO party but can log CA or Europe most days and VKs and Japan in the mornings when conditions are fair to good…
Step one is to get an antenna up. If 20′ is the limit for now it will be interesting to see how it performs. In the future, you might consider a 50′ fiberglass push-up mast with inverted Vs or lightweight options like a spider beam. The key is to get something up and get on the air.
The legs of an inverted V can be 10 to 20 degrees out of the plane with minimal impact, especially if the antenna is low. It is easy to model using 4NEC2 (it is free) to see the predicted performance. Several of us can help you get started. It is fun to design and model an antenna and then verify it on the air.
I have done a number of Antenna installs within 30’ of solar panels and only one had a noise problem. I would “sniff” the solar panel with a portable AM or AM/SW radio for starters.
73
Hamilton K1HMS
Hello Michael,
Reception on 80m and especially 160m is dominated by atmospheric noise including distant lightning. Antennas like a Beverage excel because they reject a portion of this noise more than the signal improving the signal to noise ratio (SNR).
On 40m the atmospheric noise is considerably less so cable losses, and antenna gain become more important. Unless you have a huge yagi or other high gain antenna the signal plus noise is still higher than the minimum detectable signal (MDS, sometimes called noise floor) of the majority of receivers. In most cases a Beverage would reduce the atmospheric noise to below the MDS while also reducing the signal. Unlike on 160m and 80m the SNR would be reduced which is not good.
By 20m and above cable losses, antenna gain and receiver MDS are dominate. A preamplifier is often used to improve the receiver’s MDS on 20m and above.
There are receive only antennas that work well on 40m and above. But unlike the low band Beverage it is not directly related to atmospheric noise. The goal is to improve the antenna’s gain while reducing losses. These antennas include arrays and are often at 75 ohms due to reduce cable losses. Decades ago I supplied equipment to a ITT HF station near San Fransisco. The receive array was almost a square mile.
73
Hamilton K1HMS
<p style=”text-align: left;”>Hello Harry,</p>
I have had my 2m/70cm ground plane vertical (Diamond X-50a) suspended from a high branch for years. I’m up 45′.The tip of a vertical is typically high Z so water soaked rope attached to the tip will be lossy. I used several 6″ strands of monofilament fishing line and nylon tie wraps to attach to the antenna. I have seen 3mm mastrand used.
Hamilton
Hello Rick,
Have spud gun, will travel… I’m in Amherst also, assuming you mean NH, not OH.
For a vertical dipole I use a 20oz water bottle. For a 80m iV I use two 1 liter soda bottles.
For a 40m delta loop I have a cross over rope at 96′ up between two well spaced pines with a pulley in the center. The two bottom corners are tied to trees. The rope lengths are very long over thin branches providing the strain relief. It has been up years a survived several significant wind storms and icing.
Hamilton K1HMS
Hello Paul,
I hope others can give a more specific answer.
Having managed and staffed organizations responsible for these types of systems it was rare to find someone that could address a system from end to end.
We had people that were experts on antennas, RF gear, lightning, electrical code, networks, backup power, dealing with the FCC, and more.
Some had degrees or training in electrical engineering, physics, networks, or other related fields. I had a couple of math majors and one music major and a few of the best had no formal degree. Many of the skills were taught in manufacture’s seminars and at trade conferences.
What the few that knew the systems from end to end had was a passion for the technology, hours of learning about the systems, and a lot of field experience. Many started on the clubs repeater…
Hello Peter,
If accuracy isn’t critical a meter like a Diamond SX-200, Bird, or similar with a dummy load on the output will work.
Another approach is to use a oscilloscope with a suitable probe to measure the peak to peak voltage across a dummy load and then calculate the power. This works best with a CW signal.
When high accuracy is required a precision power meter by Keysight, Agilent, or HP can be used. These use a bolometer (heat sensing) sensor and will provide accurate power measurements even with complex waveforms. These meters require calibrated attenuators or couplers to reduce the signal to a safe level.
The thing to note is the transmitter must drive into a load with a good SWR such as a dummy load, attenuator, or a well matched antenna.
73,
Hamilton K1HMS
Hello Peter,
The antenna is in parallel with the ground. At the low height the ground will reduce the impedance. Think of the ground as a resistor in parallel. Also the propagation velocity will be somewhat slower which will make the antenna appear electrically longer for a given physical length.
Both of these effects are sensitive to wave length.
At 10m you are starting at around 1/3 wavelength above ground and then raising it to over 1 wavelength at 40′. As you get past 1/2 wavelength the ground will have less effect.
At 40m the height above ground remains less than 1/2 wave and therefore Z and length will remain sensitive to height all the way up to 40 feet.
Congratulations on a nice analyzer, I also have the 55 Zoom. I wish I had BT. With BT I would hoist the antenna with the meter attached to get the Z at the feed without any transmission line effects.
Hello Luis,
Like Dave I started with a MFJ259 and traded up to a Rig Expert Zoom. The ability to see a graph is really important, especially with multi band antennas.
Another option is a nanoVNA. They are less than $50 on Amazon and can be used to over 600 MHz. It does everything a antenna analyzer does and is more accurate.
A antenna analyzer does one thing. With fewer features it can be easier to use. They are also more rugged. But they also cost six times more.
73