I have read many reports that the VHF radio in a GNS430/530/W and the GTN650/750 is nothing like as good as a standalone radio e.g. KX155/155A.
In particular, the range is said to be a lot less. That could be confirmed by the RF output power. The Garmin seems to be 10W standard, 16W optional (has anybody ever bought this option?). The King radios seem to be 10W also. So if there is a difference it would be receiver sensitivity, but their specs are exactly the same (2uV for 6db S/N).
Can anyone who has both confirm this from experience?
I have GNS530 and KX165 and it seems you’re right. I don’t have the exact proof but when I tried to compare range it seemd that King did it better. Besides that I had two Garmin radio failures in less than two month (LOC in the old box and GS in the new one).
The sound from my GNS430 is much clearer than from the KX155 next to it. Judging by the VOR indication, reception range for the NAV radio seems roughly the same. One interesting observation, however – last summer I flew in the vicinity of a thunderstorm, and the KX155 kept working, whereas the GNS430 refused to transmit or receive until we were relatively far away.
I have a KX155 and GTN650. The GTN is subjectively clearer on RX, but has had some (software) issues with squelch. No difference at all on TX.
…well this is subjective…I used to fly with Becker radio’s in my TMG with only 5W tx power and when flying through Germany VFR you had to switch from Langen to Munich and sometimes Munich was still out of reach…there you noticed the difference..btw a KX/GNC430 and a standard glider radio a la becker, dittel etc..
The GNC and GTN share the same TX/RX hardware and honestly I found the first impressions I have now the GNC more clear in RX then the KX155…….
There are so many variables in all this, quality of antenna cables’ position of the antenna etc…So I think a lot of these comments come from changing cables, antenna position etc..
just my thoughts.. 
.
I have flown quite a bit with Garmin radios (but GNS430 and 530 only) and never had an issue with the COM radio. But they were either dual installations or wired as #1 COM with #2 only used for getting ATIS and similar tasks, so I never compared them directly with other radios. And I can’t recall ever having to switch from a Garmin to the second set for better transmit or reception.
I have checked a few 430 / 530 com radio transmit and receive and call up a ground station at least 80 nm away and usually receive and transmit were both strength 5 on the 430 / 530.
My 430 com transmits through a top mounted antenna, box 2 (a King) transmits through a belly mounted antenna. Range varies on both depending on direction, etc..
My experience with the GNS Com units is good. They are very reliable and I have not had any repair required during the 13 years I have owned the GNS530. I also have a KY197A. It is a stronger radio and connected to my bottom antenna, but it is noisy thru the display and interferes with the GPS reception on certain frequencies.
The Garmin seems to be 10W standard, 16W optional
I would buy this option, if not mandatory (it is mandatory on some high end stuff). It makes a 2dB difference, which is a lot one way, but barely noticable. The difference would be minimal and the same amount of gain would could be get from using better quality cable.
Typicall a 3dB loss on coax cable is found to be acceptable. Using better coax cables, better antenna, good antenna position and good quality connectors is less expensive than 2dB on power ouput.
Better cables etc do have another advantage, which is that both transmission and receive will benefit. No reason to shout if you can’t hear the other side.
The 10W and 2uV of 6dB S/N are just minimums according standard. Actually receiver sensitivity is quite poor, compared to for example amateur radio equipment. It’s just another game. No need to have very sensitive receivers in aviation (at least not according the standard)
I have a GNS430/530W pair. Originally both were 10W but COM1 the 530W was always slightly stronger on Tx due I think to the antenna position.
Last year I managed to obtain a reasonably priced GNS430AW the 16W version (they are quite rare) which was a slide in replacement – same antenna etc,, and it has made a noticeable difference on the Tx side of COM 2 whereby I have not had to switch to COM1 on weak stations any more.
The 430AW unit came out of a King Air which had a panel upgrade, and it’s 530AW sister is still for sale, but demanding a premium, so I will not bother with it for now, although I will keep watching hoping for the market to weaken. The GNS units have great functionality, and I intend to keep mine for as long as I can, so having standby units to swapin is a great option. Long may those GTN upgrades continue. :-)
Cheers. E
