SteveShannon

Did that actually work? I understand how that would prevent the jammer from initiating access, but isn’t the jammer able to get in as soon as someone else accesses the repeater? Or was the jammer a weaker signal?

It’s an extract, not a live lookup. You can’t speed it up. It could take anywhere between a day or two to a week.

Good thinking!

I meant physically measure the element and compare it to the length mentioned in the video.

You can still check it to see how it is cut.

By the way, here’s a video about tuning the Tram 1486:

Correct

I agree; that’s completely different. “Tuning Step” sets incremental frequency change when you’re in VFO mode and press either the up or down arrow That’s really only important for VFO tuning. Because the bandwidth and the center frequency for all 30 channels are preordained by regulations, “Tuning Step” is immaterial to GMRS and can even cause problems. The channels in GMRS are not sequential and have differing bandwidths. Some channels are interstitial even. Here’s the list of GMRS channels: https://mygmrs.com/help/about-gmrs

It depends on the antenna, but for a single band whip antenna without a trap you “simply” adjust the length of the antenna until it matches the frequency you wish to transmit and receive. Connect an analyzer to your antenna and look to see where the dip is. If the dip is at a lower frequency than desired your whip is too long. Take off a tiny bit and check again. The dip should have moved to a slightly higher frequency. If taking off a half inch changes the resonant frequency by 2 MHz (I made that number up; you’ll have to figure it out for your situation. It could be less or it could be more!) and you only want to change 500 kHz then you’ll need to take off an eighth of an inch more. Approach it very carefully because it’s damned hard to make the radiator longer. Most antennas that are intended to be tuned will have some sort of instructions and maybe a cutting chart. Here’s a video on tuning the Tram 1486 to GMRS frequencies:

If you can borrow an antenna analyzer capable of UHF hook it directly to the antenna. Then tune the antenna to the frequency you want. Tune it before adding coax. Coax will just make it look better unless the coax is damaged or the wrong impedance.

Thanks, Rich!

When your radio is set to TSQL it sends a tone while transmitting and it remains quiet (squelched) during receive unless exactly the right tone is received. When it’s set to Tone, it sends the tone but it doesn’t require one when receiving.

I’ve reported this issue to Rich. He’s usually pretty fast about responding.

Then it really comes down to the RX tones or frequencies used. If you’re transmitting directly from your HT to your Retevis you must be using a simplex channel and I recommend doing that without any tones at first. I always recommend minimizing the number of moving parts that must line up. Tones are useful in minimizing interruptions but can add confusion. Especially when communicating via simplex turning off tones can help you diagnose other problems.

My Midland mount works fine on my 4Runner.

Great point! A bad speaker jack could do that.

Most modern radios can withstand an SWR well over 2.0:1 without damage. You can calculate the SWR at the antenna based on the losses you have calculated. Your SWR meter calculated 1.8:1 with the lossy cable, but that doesn’t include the losses for both forward power and reflected power. You calculated that 63% of the power is attenuated. I’m going to use 100 watts as the RF output just to make the calculations easier. With a 50 watts transmitter the values would be half. Your radio transmits 100 watts. You calculated 63% loss so 37 watts arrives at the antenna. So, this is why the measurement location matters. At the radio Forward Power is 100 watts and by the time it gets to the antenna Forward Power has been attenuated down to 37 watts. Due to an impedance mismatch some portion of the Forward Power reflects from the feedpoint and heads back towards the radio. That’s the Reflected Power. Again there’s a 63% loss before it arrives at the radio. Loss is loss for both Forward and Reflected power. Here’s an interesting article about SWR that correlates reflected power percentage to SWR in a table: https://www.arrl.org/files/file/Technology/tis/info/pdf/q1106037.pdf You measured an SWR of 1.8:1 (I assumed at the radio). That correlates to 8.2% reflected power. So, at your hypothetical radio, when transmitting 100 watts forward, 100 watts was seen as the Forward Power and 8.2 watts was seen as the Reflected Power and an SWR of 1.8 was calculated from those two values. But we know that 8.2 watts is the Reflected Power measurement after losing 63%, so 8.2 watts is really 37% of the actual Reflected Power (call that RP). As an equation 8.2 = 0.37 * RP. Rearranging, RP = 8.2/0.37. Solving, RP is 22.16 watts actually reflected at the feedpoint. But only 37 watts even made it to the feedpoint. So an accurate calculation of SWR at the feedpoint would be based on the Forward Power of 37 watts and Reflected Power of 22.16 watts. Again looking at the table in the ARRL article, the reflected power percentage is 22.16/37 or 59.9% and that calculates to an SWR of 7.85:1 (I used the online SWR calculator at https://www.aareff.com/en/calculating-swr/?srsltid=AfmBOoqd-GzPr7AeD9xpbmFecxHoSzzTGyKbeLlR00b78uweI9rYUxED) That doesn’t seem right to me if you’re using an antenna tuned for GMRS frequencies. Please check my math.

So the actual SWR of the antenna is almost certainly already higher than 1.8. No, I wouldn’t recommend not upgrading the coax. Lossy coax simply hides high SWR. The “right” thing to do depends on your resources. I would measure the SWR of the antenna right at the antenna feedpoint and adjust the antenna (tune it) until it’s as close to 1.0:1 as possible at the frequency you intend to transmit most often. I’ll have to go back and see what antenna you’re using and whether it’s one that can be tuned. Then, your reflected power will be reduced to the minimum and the attenuation of reflected power will have no effect on the apparent SWR.

I’ll correct my explanation to emphasize that the SWR is not actually going up, your measurement of reflected power is becoming more accurate. As a result the SWR value calculated at your radio will become higher, but in reality it has been the actual SWR hasn’t changed. You’re just seeing a more nearly accurate calculation. In other words, your SWR is higher than what you’re seeing and changing to the better cable will reveal that.

One thing to be aware of is that SWR will appear to go up, possibly by quite a bit. Here’s why: SWR is calculated using forward transmitted power and reflected power. At your radio the forward transmitted power is the maximum. Attenuation in your cable reduces it as it travels along the cable until it finally arrives at the antenna. There, any mismatch in impedance causes a portion of the power to be reflected back towards your radio. Again, attenuation robs power from the reflected power as it travels back towards your antenna. Your radio or a SWR/wattmeter measures the forward and reflected power wherever it’s inserted into the feedline. So, any power measurement done at the radio will measure the lowest possible reflected power and utmost forward power, which results in a calculation of SWR that’s not accurate. Let me emphasize that the actual SWR of the antenna doesn’t change, but because forward and reflected power are being measured at the radio, the calculated value of SWR is incorrect. Replacing the lossy 7 mm cable with less lossy 10 mm cable will result in less attenuation both ways which will result in a higher (but more nearly accurate) calculation of SWR. Of course the most accurate place to measure power is right at the feedpoint of the antenna, where the actual forward power delivered to the antenna and the actual power reflected by the antenna can be measured most accurately, but it’s almost always inconvenient to do so.

Have you ever received anything on the RA-87? There are only four reasons your RA87 wouldn’t receive from your HT and MXT500: wrong tone, desense, wrong frequency, or broken receiver. You undid setting Tone Mode to Tone when you set the RX Tone to 123.00. Set Tone Mode to Tone and leave the RX tone clear. Setting the RX tone to something is the same as setting TSQL and filters your incoming signals. Leaving your RX tone clear and setting Tone Mode to Tone tells your radio not to filter on tones but to allow everything through.Red redemption. When you’re troubleshooting reception problems you want to start by let everything in. Setting Tone Mode to Tone tells your radio to send a tone on transmit, but to let everything through on receive. Most times when someone cannot hear transmissions from another transmitter it’s because they have the wrong tone set for RX. Another common reason not to receive from another radio is because you’re too close to the transmitting radio and your receiver is desensing. Make sure your transmitting radio and receiving radio have some distance between them. Finally, if you’re not too close and you’re not filtering on tones and you still don’t receive things on your RA-87 maybe the RA-87 doesn’t receive. Have you ever received anything on the RA-87?

Change to Tone instead of TSQL.

Swapping in better coax certainly won’t hurt. I agree that a 63% power loss is substantial. What’s the projected power loss after swapping?

The db20g is not accessible through Chirp.

No