Rookie question!

[Wericha]

I have recently joined the GMRS world with a pair of UV-5X radios. In setting them up for repeater access I’ve hit a problem I cannot figure out. I’m probably missing something glaringly obvious.

A local repeater is open and uses CTCSS 141.3. Both radios are programmed identically. When I do a simple dead key, both radios receive the repeater carrier after I release the PTT. The status light on both radios comes on during the carrier signal, but not while the PTT is pressed. However, when I speak the other radio does not receive any transmission and the status light does not come on to indicate channel traffic. Both radios then receive the carrier signal, and the status light comes on, after I release the PTT. The radios are at least 10’ apart when I do this.

Both radios send and receive properly on all other channels.

What am I missing?

[MichaelLAX]

They are still too close to each other. 

[Wericha]

18 minutes ago, MichaelLAX said:

They are still too close to each other. 

How far apart must they be?

Why doesn’t the same behavior occur in simplex mode? I can have the radios within inches of each other, on say Ch 22, and they both send and receive.

[MichaelLAX]

Those are good questions:

The least expensive, usually from China, hand-held radios ("HT"), use what is known as SOC technology: System on a Chip - The whole radio is virtually built into one chip.

Most of the more expensive radios (usually 3X the cost and more), have additional circuitry known as a superheterodyne circuit.  This gives the receiver both more selectivity (the ability to differentiate between two powerful signals on two close frequencies) and sensitivity (the ability to pull in more distant and/or weaker signals).

In simplex mode: one HT is transmitting on a frequency and the other HT is receiving on the same frequency. There is no second transmission to overwhelm the receiver of the second HT; only the one signal.

In repeater mode, the first HT is transmitting on 467.abcd up to the repeater; and the second HT is receiving the retransmitted reception signal from the repeater on 462.abcd.

The second HT must differentiate between two received signals: the signal you want to receive on 462.abcd from the repeater many miles away, and the HTs more powerful signal on 467.abcd.  Hence the HTs signal washes out the reception of the repeater's signal on the second HT.*

Superhetrodynes have that ability; SOC's do not.

How much is far enough away?  Differing factors are at play here: The power of the HT transmitter; the distance between the HTs and the distance and power from the repeater.

Experimentation will help you determine the answer.

*NOTE: this is why when two inexpensive HTs are bundled together with the appropriate cabling and settings to act like an inexpensive semi-portable repeater, they must be on the two separate Ham bands: 2 meters (144 MHz) and 70 cm (440 MHz) to avoid this washout effect.

[Wericha]

9 minutes ago, MichaelLAX said:

Those are good questions:

The least expensive, usually from China, hand-held radios ("HT"), use what is known as SOC technology: System on a Chip - The whole radio is virtually built into one chip.

Most of the more expensive radios (usually 3X the cost and more), have additional circuitry known as a superheterodyne circuit.  This gives the receiver both more selectivity (the ability to differentiate between two powerful signals on two close frequencies) and sensitivity (the ability to pull in more distant and/or weaker signals).*

In simplex mode: one HT is transmitting on a frequency and the other HT is receiving on the same frequency. There is no second transmission to overwhelm the receiver; only the one signal.

In repeater mode, the first HT is transmitting on 467.abcd up to the repeater; and the second HT is receiving the retransmitted reception signal from the repeater on 462.abcd.

Hence the second HT must differentiate between two received signals: the more powerful signal from the HT and the signal from the repeater many miles away.

Superhetrodynes have that ability; SOC's do not.

How much is far enough away?  Differing factors are at play here: The power of the HT transmitter; the distance between the HTs and the distance and power from the repeater.

Experimentation will help you determine the answer.

*NOTE: this is why when two inexpensive HTs are bundled together with the appropriate cable and settings to act like an inexpensive semi-portable repeater, they must be on the two separate Ham bands: 2 meters (144 MHz) and 70 cm (440 MHz) to avoid this washout effect.

Hmmm….interesting.

Thanks for the explanation, although some of it still does not make sense to my novice brain. I’ll have to spend some time on that for it to sink in. But it also reinforces the old adage of getting what you pay for. In time I may look into better quality radios. A definite deficit to these is the lack of weather durability, kinda defeats the purpose of emergency communications if they are only designed for pristine conditions.

I guess I’ll have to send my wife to the front yard with a radio……

[MichaelLAX]

6 minutes ago, Wericha said:

But it also reinforces the old adage of getting what you pay for...

Exactly!

There are also relatively inexpensive HTs from China that have water-resistant and even waterproof specifications.

Check out OffRoaderX's detailed YouTube reviews of the various HTs available and he does focus on their water-resistant abilities:

https://www.youtube.com/results?search_query=notarubicon

[mrgmrs]

MichaelLAX, you're explanation of desense, and especially the difference between simplex and repeater behavior in that context, is very well written.

[AdmiralCochrane]

Very good explanation.  When our local elmer gives a Tech class one of the last day hands on class demonstrations is each student actually using HT's brought in by other club members under their direct supervision.  This is done in the parking lot right under the repeater. Probably half of the HT's are CCR's but I have never noticed a desensing problem during the class demonstration.  I guess we have been lucky with the hardware volunteered. 

[MichaelLAX]

On 9/13/2021 at 2:12 PM, AdmiralCochrane said:

This is done in the parking lot right under the repeater…

Thank you both!

there is your reason:

you are so close to your repeater, it’s more powerful signal is received by the other HT and not washed out. 

[fillmoreranger]

On 9/12/2021 at 9:28 AM, MichaelLAX said:

Those are good questions:

The least expensive, usually from China, hand-held radios ("HT"), use what is known as SOC technology: System on a Chip - The whole radio is virtually built into one chip.

Most of the more expensive radios (usually 3X the cost and more), have additional circuitry known as a superheterodyne circuit.  This gives the receiver both more selectivity (the ability to differentiate between two powerful signals on two close frequencies) and sensitivity (the ability to pull in more distant and/or weaker signals).

In simplex mode: one HT is transmitting on a frequency and the other HT is receiving on the same frequency. There is no second transmission to overwhelm the receiver of the second HT; only the one signal.

In repeater mode, the first HT is transmitting on 467.abcd up to the repeater; and the second HT is receiving the retransmitted reception signal from the repeater on 462.abcd.

The second HT must differentiate between two received signals: the signal you want to receive on 462.abcd from the repeater many miles away, and the HTs more powerful signal on 467.abcd.  Hence the HTs signal washes out the reception of the repeater's signal on the second HT.*

Superhetrodynes have that ability; SOC's do not.

How much is far enough away?  Differing factors are at play here: The power of the HT transmitter; the distance between the HTs and the distance and power from the repeater.

Experimentation will help you determine the answer.

*NOTE: this is why when two inexpensive HTs are bundled together with the appropriate cabling and settings to act like an inexpensive semi-portable repeater, they must be on the two separate Ham bands: 2 meters (144 MHz) and 70 cm (440 MHz) to avoid this washout effect.

Thank you! This is the best explanation I have read to date on the differences between superheterodyne vs SoC transceivers. I am brand new into GMRS and recently received my license. I trying to soak up as much education as I can, to make intelligent decisions going forward. I have been looking at Wouxum HT’s for my first radios. Based mainly on reviews from our favorite YouTube Hobo, I was leaning towards a KG-935G. While it has very appealing bells and whistles, I was surprised (disappointed?) to learn it is a SOC radio… unlike the 805G/905G’s. I am wondering if I may be better served with a superheterodyne 905 vs the SoC 935?

Thoughts?

[TOM47]

1 hour ago, fillmoreranger said:

Thank you! This is the best explanation I have read to date on the differences between superheterodyne vs SOC transceivers. I am brand new into GMRS and recently received my license. I trying to soak up as much education as I can, to make intelligent decisions going forward. I have been looking at Wouxum HT’s for my first radios. Based mainly on reviews from our favorite YouTube Hobo, I was leaning towards a KG-935G. While it has very appealing bells and whistles, I was surprised (disappointed?) to learn it is a SOC radio… unlike the 805G/905G’s. I am wondering if I may be better served with a superheterodyne 905 vs the SOC 935?

Thoughts?

I HAVE ALL THREE, THE 805G/905G/95’s. AND HEAR NO DIFFERENCE IN TX  OR RX!  THE KG-935G IS MY FAVOEITE DUE TO THE DISPLAY.  i EXPECT UPS TO DELIVER ANOTHER KG-XS20G THIS WEDNESDAY!  THE ORDER FOR THE SECOND KG-935G STILL SHOWS "PROCESSING" ON BACKORDER.

[MichaelLAX]

You're welcome!

Tom's experience is good, since he has experience with both superheterodyne and a SOC HT.

I have only SOC radios, so my experience is not a good test.

I will say that living in the Los Angeles area with many GMRS/FRS simplex and repeater users, I have not noticed any problems and I get what I pay for.

If you can afford the difference, then undoubtedly, a superheterodyne radio is the best buy!

My philosophy with a new technology hobby, is to start off reasonably inexpensively; gain knowledge and experience and then sell it off (or give it away) and upgrade at that point!