“Wow! I just got another transceiver. I’m gonna need a coax switch. I’ll get a used switch off the web.”

Bad idea… Used coax (coaxial) switches come in all conditions. A few will be like new. Others will have burned contacts from surges and arcing, corrosion that can’t be easily removed, worn silver on the switch contacts, slop in the switch mechanism and many other ills. Why would you want to connect your high-quality transceiver through a junk switch that could present a high SWR, or worse?

Quality coax switches have high isolation (typically in excess of 50 dB), low RF resistance (insertion loss), low VSWR and firm, crisp switching. Isolation is very important when switching two or more rigs to the same antenna. RF leakage from one switch port to the other can overload and even damage other radios in the system. As long as the ports are well isolated from each other, that problem is controlled.

Insertion loss reduces your received signal and creates heat (resistive loss) in your transmitted signal. Normally, a few tenths of a dB is easily tolerated. As frequency increases, insertion loss usually does, too. A switch with 0.2 dB insertion loss at 3.5 MHz may be well over 1 dB on two meters! It’s important to look at the full specs.

Switch SWR is also important. We all want our antennas to operate at maximum efficiency. That usually means watching our SWR. A good switch will have an SWR of less than 1.2:1. This rating goes back to insertion loss; the lower the SWR the lower the insertion loss will be, and vice versa. Again, SWR normally increases with frequency.

Mechanical design is also very important. You want the switch to feel solid and to have crisp motion when the switch is used. Avoid lightweight switches with sloppy switch mechanisms. Robust mechanical feel is usually a good indicator of internal construction.

Coax switches have limitations on maximum RF frequency and power. DON’T rely on engineering fudge factors here. Exceeding these ratings can cause outright switch failure and damage to your gear!

 

Advertisements

Tinned-copper braid has been around for a long, long time. It’s been used in many grounding applications because of its flexibility and ease of soldering. It’s great for grounding radio chassis to radio chassis (DXE-TCB05-RT01) or from your equipment to a single-point ground. Good stuff. (DXE-TCB-050)

Copper strap is better than wire because it reduces RF skin effect with the very large surface area it presents.

There is a problem with braid: it retains water. The fact that it will hold water causes corrosion to the tinning material and, eventually, the copper. This may not be a problem in New Mexico but it is in many parts of the US and the World. Tinned-copper corrosion is evident when the braid begins to turn green.

That’s where copper strap comes in! For grounding connections that go outside the building and into the weather, the better choice is copper strap. Copper strap (GCL-1220-025) dries quickly, its oxidation actually protects the strap, and it will far outlast copper braid when used for the same outdoor application. Copper strap also reduces RF skin-effect resistance over the use of wire.

So, which is best? Both! Use convenient and flexible braid in the shack to accomplish your equipment grounding needs. Then transition to copper strap to go outside the shack and into the weather.

 


Q: If RF is a high frequency AC signal, why are there plus and minus signs on a balun?

A: Keep in mind that we are usually connecting a ‘BALanced’ antenna to the ‘UN-balanced’ coaxial cable, hence the term BALUN. So, for most regular applications on a single antenna that is ground independent, such as a beam, dipole and many other wire antennas, the balun polarity doesn’t matter. However, polarity markings on baluns become very important for matching phase on multiple antennas in a phased array, such as stacked Yagis. Also, on most 1:1 baluns, the minus side is connected to the coax shield. So, for an antenna that is ground dependent, such as a vertical, Inverted-L or long wire that uses a ground radial system, the positive terminal must be connected to the radiating element and the negative terminal must be connected to the radial system.


ICOM IC-7300 HF Plus 50 MHz Transceivers IC-7300

My new ICOM IC-7300 transceiver has been loads of fun, but the scope was not
displaying the frequency correctly for signals I was copying. I was listening to a
local AM signal on 570 kHz and had to offset the frequency display by 1 or 2 kHz
to have it sound intelligible. Also, the CW signals I had copied on 40 and 20 meters
did not line up exactly.

I installed the latest firmware version (1.14). You can do this by following the
instructions in chapter 15 of the full manual. The update solved the CW issue and
the signals on the scope were exactly where I expected them to show up. To my
horror, there was no improvement with the AM stations. This was very
discouraging and I was just about ready to send my 7300 back to ICOM!

At about the same time, it occurred to me that maybe there was a setting that
may have gotten changed inadvertently. The manual says this could be caused by
“static electricity or other factors” (probably me). I decided to do a reset which
was fairly simple:

1. Tap the “menu” button
2. Tap the “set” button.
3. Tap the “others” button
4. Tap reset.
5. Tap the “All reset” button and follow the on-screen instructions.

“All reset” clears all data and returns all settings to their factory defaults. If you
have settings or memories you want to save, you could try a “partial reset” first
and try the “all reset” if that doesn’t work. I went to the “all reset.” You can also
save your settings to an SD card prior to the reset (recommended).

The reset solved the problem with the scope and copy of AM signals. I know of
other people who had this problem, so I hope this can be of help to you.
73 and enjoy your IC-7300!

Author: Dave Fairbanks, N8NB, DX Engineering


We received a question from a Ham in Oklahoma about mounting a Cushcraft R8. Although our answer was aimed at the Cushcraft R8, the information can be used for other vertical antennas that are mounted above ground.

Cushcraft recommends that the R8 antenna be mounted at least 10 feet above ground level.

The mast you should use depends on your soil conditions. Here in NorthEast Ohio, I suggest using a post hole digger to make a hole about 12″ in diameter  and about 3 feet deep, and use a 1.5″ water pipe (which is just under 2″ OD) about 5 feet long with threads on one end. Put some gravel in the bottom of the hole for drainage, brace the mounting
pipe with the threaded portion up, and use quick-crete (you pour the dry stuff in the hole, then add water and stir with a stick). It sets up in about 20 minutes – so make sure that mounting pipe is straight up and down so the antenna won’t be leaning. This is pretty much the system I used for my 43-foot ground mount vertical. Using the threads, I could then mount another water pipe to it using a threaded coupler, and then mount the antenna on the extended pipe.

Would I use guy ropes? – YES. And in Oklahoma , a Big YES – you guys get a lot of wind! Any vertical antenna should be guyed. You can use a very light weight rope and make the guy ropes somewhat snug – not real tight. Take a look at the DX Engineering guy rope kits – they may be what you are looking for. I used a four-point guy rope scheme on my 43 foot vertical iwth no problems after 8 years of Ohio wind storms.

DX Engineering OMNI-TILT™ Vertical Antenna Tilt Bases DXE-OMNITILT-2PAnother great option that allows easy up/down for tuning, maintenance ,or in case of severe weather, is to use a tilt base. We suggest the OMNI-TILT Base. There are many tips in the manual about installing and using a Tilt Base, which can be found here. You may decide this is another option to use for the mounting pipe going to the antenna.

– Tom Parkinson, KB8UUZ


If no one is on the repeater and you would like to start up a conversation, simply call the station you wish to talk to. Say “KD8XXX, this is KE8XXX calling.”

Or, if you want to put out a general call to anyone, simply key up and say your call sign.

Don’t be a “kerchunker” on the repeater. A “kerchunker” is someone who keys up the repeater just to hear the repeater courtesy tone.

Don’t call CQ to initiate a conversation on a repeater. Just listen to make certain the repeater is not in use. Then key your microphone, and say your call sign: “KE8XXX” then “listening.” If someone happens to be listening and they want to talk to you, they will respond.

Happy hamming!


ERICO CADWELD ONE SHOT Wire to Ground Rod Clamps GT1-161L

ERICO CADWELD ONE SHOT Wire to Ground Rod Clamps GT1-161L

A “Cadweld One Shot” is ideal for making permanent, reliable connections to your ground rods. It’s a very cool process that is easy to do and will impress even the staunchest members of your radio club!

Using a “One Shot” will provide a very high quality exothermic connection for all of your outdoor ground rod applications. “One Shots” make quick work of ensuring your ground system is the best it can be.

The “One Shot” is a convenient, single-use ceramic mold and welding material connection package. They produce a non-removable, permanent, exothermic connection to a ground rod that will not loosen, corrode or increase in resistance for the life of the installation. They are not clamps, but replace a clamp with a welded connection that thermally fuses the wire to the ground rod. Get you some of THAT!

“One Shots include convenient, single-use (one shot – get it?) ceramic molds that eliminate the need for any type of clamps and/or frames that can loosen or degrade over time. These exothermic connections are ideal for copper-bonded steel, galvanized or stainless steel ground rods.