KENWOOD® TH-D72A vs vx-8gr

[SteveF]

Ok - probably going to get one of these in the next 1 to 3 weeks (friday probably) and after looking at specs and talking to Troj at a recent meeting he mentions he bought the 1800mAh battery pack as it sucked the battery in GPS mode. I see the kenwood comes with an 1800mAh battery and once you figure in the cost of the extra battery for the yaesu then the price diff is a lot less - about $30-$40 more for the kenwood.

So I am leaning towards the Kenwood - can anyone who has the kenwood verify it has the bigger battery pack and lasts the better part of the day using the GPS and not much talking?

 

[n5wd]

...an anyone who has the kenwood verify it has the bigger battery pack and lasts the better part of the day using the GPS and not much talking?

Steve,

Unless there's something out there that I'm not aware of, the stock Kenwood PB-45L battery (1800 mAh @ 7.4v) is the only battery available for the D-72. I have used mine on a weekend running around the D/FW metroplex, "smart beaconing" (sending APRS packets), and of course, having the internal GPS going, for about 8 hours with the occassional voice transmission before the battery gave up. Granted, I wasn't talking on it very often, but I did have a couple of short QSO's on it during that time.

I'm glad I went with the D-72 over the 8-GR, primarily because I CAN hook it up to a computer or external GPS. But, if I were to change anything, the tracking window in the D72 wastes a bit of space showing the APRS symbol that the station is transmitting, resulting in a smaller compass-rose and bearing indicator than the VX-8GR has, judging by the screen shots I've seen. Other than that...

BTW - If you plan on getting the D-72, also plan on getting one of the many SMA-BNC adapters that are available. Less strain on the D-72's SMA antenna connector, and fits more things, like an Arrow antenna BNC connector.

73 Wayne N5WD

 

[WillMarchant]

It comes stock with a 7.4V 1800 mAh 14 Wh Li-Ion pack. Seems like it lasts a long time. Buy the AA/AAA battery holder to go with either.

 

[SteveF]

thanks - just making sure kenwood didnt change battery packs - only see the 1800mAh one as opposed to the yaesu with only 1100mAh standard and 1800 extra

 

[SteveF]

well I went ahead and ordered the kenwood earlier today - now I got to save my pennies for a couple of weeks and talk to big red bee

 

[WillMarchant]

I've been pleased with mine, so far. Take a look at https://ariss.net/ for something else you can use it for...

 

[JimJarvis50]

I got the 8GR because i couldn't wait for the kenwood. It's a fine radio best as I can tell. I have it mounted on a yagi. What I'm doing is running both a Bigredbee gps and an RF tracker coming into the two receivers on the radio. I haven't flown it that way yet, but I think it's going to work just fine.

Jim

 

[troj]

Creative idea, Jim, and one I never thought of!

-Kevin

 

[n5wd]

I got the 8GR because i couldn't wait for the kenwood. It's a fine radio best as I can tell. I have it mounted on a yagi. What I'm doing is running both a Bigredbee gps and an RF tracker coming into the two receivers on the radio. I haven't flown it that way yet, but I think it's going to work just fine.

Hey, Jim... didn't realize you were also a ham.

Here's something you might consider, especially if you have a yagi that has both 2m and 440MHz elements, like the Arrow 2m/70cm satellite tracking yagi (7 el on 70cm and 3 el on 2m). Instead of using the diplexer that combines both the 2m and 70cm into one coax cable (which it's normally doing running into a radio that runs duplex so that you can talk to the satellites on 70cm and hear your signal come back at the same time on 2m).... instead... run two pieces of coax to two HT's, one set up on 70cm (probably the Bee tracker) and one set up on 2m (the BLGPS operating on some other frequency than the national APRS frequency of 144.390MHz). Something like that, though a bit heavy for one-handed operation, would be the "Bee's Knees".... :lol:

I'm considering something like that for a big project, where the payload and nosecone will probably separate from the booster... both of which will have the ability to be RF tracked: one with the GPS, the other with the standard tracker.

 

[JimJarvis50]

Creative idea, Jim, and one I never thought of!

-Kevin

I was really just looking for a way to get better "reception" for the gps signal. i didn't want to use a yagi for the gps only in case I didn't know where to look. But with the tracker, I know the direction and so I should know where to point the gps. I'll have to learn to use the tracker differently (I normally search for the nulls and not the stongest direction). Hearing the two signals at the same time is no problem. I'm just waiting for a launch to get some practice.

Wayne, you're a bit ahead of me on the technical side. What I have is the arrow 5 element yagi and attenuator. I listen to both signals on 70 cm, but at different frequencies. With the two receivers, I can set the squelch, volumes, etc., at what works best for each device (although the gps has to be brought in on the B receiver). Like I said, I think it will work pretty well.

Jim

 

[n5wd]

I was really just looking for a way to get better "reception" for the gps signal. i didn't want to use a yagi for the gps only in case I didn't know where to look. But with the tracker, I know the direction and so I should know where to point the gps. I'll have to learn to use the tracker differently (I normally search for the nulls and not the stongest direction). Hearing the two signals at the same time is no problem. I'm just waiting for a launch to get some practice.

Wayne, you're a bit ahead of me on the technical side. What I have is the arrow 5 element yagi and attenuator. I listen to both signals on 70 cm, but at different frequencies. With the two receivers, I can set the squelch, volumes, etc., at what works best for each device (although the gps has to be brought in on the B receiver). Like I said, I think it will work pretty well.

It should work quite well, but I predict you'll soon find you don't need the traditional tracker much (unless you're tracking two different pieces that have separated)... the GPS packets, when decoded by the 8GR, will show you which way to point, and how far away it is. That's the beauty of GPS in a rocket!

 

[WillMarchant]

It should work quite well, but I predict you'll soon find you don't need the traditional tracker much (unless you're tracking two different pieces that have separated)... the GPS packets, when decoded by the 8GR, will show you which way to point, and how far away it is. That's the beauty of GPS in a rocket!

And you can use the data packets themselves to "DF" based upon amplitude and quality. So, even if you can't decode the packets, you should be able to get a bearing to your rocket.

I'm not arguing against the "belt and suspenders" principle of having multiple tracking devices!

 

[JimJarvis50]

It should work quite well, but I predict you'll soon find you don't need the traditional tracker much (unless you're tracking two different pieces that have separated)... the GPS packets, when decoded by the 8GR, will show you which way to point, and how far away it is. That's the beauty of GPS in a rocket!

I hear what you guys are saying, but I believe I can significantly increase the reliability of recovery using this approach. My experience is that at some point above a range of about 5 to 10 miles, the gps radio signal is either not present or is not valid. This depends on the situation of course, the antenna, the nose cone and materials, etc. If the signal is lost for a significant period of time, you don't have a valid gps location, and I don't think it's a good idea to be using a yagi to reacquire the gps signal. That forces an omidirection antenna.

My experience is also that a tracker will always be the first line of defence in locating a rocket - it's simply more reliable than gps. I normally use both, but this requires a separate tracking radio and antenna, and split attention during the flight. By combining these into one radio, I reduce the amount of equipment, I get the benefit of the yagi for the gps, and I have everything I need right in front of my nose. I do need some more practice before I can declare victory here, but I'm pretty confident in the approach at the moment.

Jim

 

[troj]

My experience is also that a tracker will always be the first line of defence in locating a rocket - it's simply more reliable than gps. I normally use both, but this requires a separate tracking radio and antenna, and split attention during the flight. By combining these into one radio, I reduce the amount of equipment, I get the benefit of the yagi for the gps, and I have everything I need right in front of my nose. I do need some more practice before I can declare victory here, but I'm pretty confident in the approach at the moment.

It's also much easier to track via a conventional transmitter with a more steady transmission sequence than it is to track via APRS, when using fox hunting techniques.

I also agree, completely, on the "less stuff to carry"! My first method was with a PicPac to decode the APRS packets. While it works very well, it's just one more thing to haul along with me..

This is the same reason why I don't care for solutions that use a laptop to decode the packets. If your 'base' isn't in a spot to get a good packet, then you have to haul all of the equipment to a location that is.

I really like your approach, Jim. And the -8GR is a great radio for it!

-Kevin

 

[n5wd]

I do need some more practice before I can declare victory here, but I'm pretty confident in the approach at the moment.

Like I said... I'm sure it'll work, great! Be sure and get some videos with good audio of the signals you're hearing - wold love to see how it works for you. And, as my TH-D72 is also a dual receiver, you've made me re-think the two-HT approach as well. Hmmmm..... That's why I LOVE these forums! Great ideas from great minds.

73 Wayne N5WD

 

[ksaves2]

The other option with the D72 or a D7A(g) is one can use a palmtop
or laptop and plot a flight in real time. Once landed, one can pull it out of the laptop and go after the rocket. The D7A(g) can do a little trick the D72A can't with a program called Xastir. One can plug their GPS receiver like a Garmin 60CsX or Cs, directly into the D7A(g) and have the D7A(g) plugged into the laptop via a USB/serial converter. Xastir will use the position data from the 60CsX that is plugged into the A(g) for bearing information. You can preset the 60Cs to navigate "to" the rocket before launching and have a Datum line pointing to the rocket. Once landed, you can pull out the serial cable from the D7 and go track with the D7 and the 60CsX if need be. This is an undocumented TNC command that can be placed in Xastir.
This pass-through is not available with the 72 and some are hoping it might be possible to activate it with a firmware upgrade. There are no guarantees though.

If one needs more power from a larger rocket, use a Byonic MT-300. At 300mW it has plenty of power though one has to consider the larger batteries required. Also, DO NOT PAINT THE ROCKET WITH METALLIC PAINT! If you have the tracker antenna buried in the Ebay. Metallic paints soak up Rf

 

[SteveF]

got the kenwood last week - got it decoding APRS packets without too much difficulty. should be ordering the big red bee in the next day or 4

 

[jsdemar]

I just got the VX-8GR handheld a couple days ago. The TNC and GPS are build into it. It didn't take much to configure it with my call sign and get it sending APRS packets. Also, hook up the USB cable to the PC and it'll echo APRS packets or GPS NMEA strings back to any program to log or display.

Nicest feature is the compass heading and distance on the display to show where the APRS transmitter is located. I can set up the BRB at home and drive around and it shows the distance and direction to my house. Looking forward to a rocket flight test! I also have a FT7900R mobile and TinyTrak4 that I could setup with a laptop as a logging/mapping station. But, the little VX-8GR is all you need to hike around looking for the rocket.

-John
(KF5JUD)

 

[Ethan]

Jim, I was having the same thoughts as you (too scared to rely on a yagi with the gps in case I had no idea where to search), and tried out your idea with the 8GR mounted on the yagi and both beeline TX and GPS coming into the unit. It seemed to work well, I only found one real issue (for me)...

At 16 miles, with 7 element yagi and VX-8GR, there was a very narrow window for decoding the GPS packets (more or less had to have the yagi pointed directly at the transmitter). However, the TX signal was still very strong, and even with maximum squelch there was probably a 90 degree window (vertical and horizontal) at which the signal could be received. So its not really directional enough to be of great assistance in finding the GPS transmissions.

I added a arrow antennas 4Mhz offset attenuator into the setup, but apparently even just adding the unit into the circuit creates enough attenuation to kill of any signal from both transmitters. So scratch that idea.

Does anyone have any ideas regarding the above....hopefully it makes some sense.

John, do you have the link/part number for the USB cable?

Regards
Ethan

 

[jsdemar]

John, do you have a link/part number for the USB cable?

It's the CS-VX8GR-USB software and cable combo. The cable alone has the Yaesu part number USB-82.

 

[ksaves2]

Join the VX-8R yahoo group and search for this topic:

Using a Garmin GPS with VX8-GR

There is a long thread on cables and some of the cables for the D7A(g) will work with the GR. It started on 12/31/10 Can pick up some cheaply on Ebay.

The GR is cheaper than the 72 and $GPWPL words can be had out of the dataport
of the GR. One could technically take the DB9 cable from a D7A(g) and use a USB/serial converter to get a tracking program to plot the positions on a laptop or a handheld GPS. With a program like Xastir, one could record the flight for later playback.

The Kenwood D7 to Garmin 60Cs or CsX cable will work with the GR. See that thread I refer to above.

The D72 and D7A(g) have more direct access to the TNC and it is not absolutely necessary for those satisfied with tracking by a compass rose arrow bearing and a distance. Seeing that one has to cross so many roads or the rocket is getting close to a lake or stream:shock: is where the real time mapping option comes in.

For instance with the D7A(g) Garmin 60Cs combo the rocket can be locked in on the pad and the Garmin told to "navigate to" the rocket/waypoint. As long as packets are coming in, the datum line will point towards the rocket. If the Rf link is lost, it continues to point in the direction of the last known packet. Can scroll back and forth to the map and the datum line. Really neat stuff. Kurt

 

[lmt56]

Steve,

Unless there's something out there that I'm not aware of, the stock Kenwood PB-45L battery (1800 mAh @ 7.4v) is the only battery available for the D-72. I have used mine on a weekend running around the D/FW metroplex, "smart beaconing" (sending APRS packets), and of course, having the internal GPS going, for about 8 hours with the occassional voice transmission before the battery gave up. Granted, I wasn't talking on it very often, but I did have a couple of short QSO's on it during that time.

I'm glad I went with the D-72 over the 8-GR, primarily because I CAN hook it up to a computer or external GPS. But, if I were to change anything, the tracking window in the D72 wastes a bit of space showing the APRS symbol that the station is transmitting, resulting in a smaller compass-rose and bearing indicator than the VX-8GR has, judging by the screen shots I've seen. Other than that...

BTW - If you plan on getting the D-72, also plan on getting one of the many SMA-BNC adapters that are available. Less strain on the D-72's SMA antenna connector, and fits more things, like an Arrow antenna BNC connector.

73 Wayne N5WD

Lets talk antenna up grades for the D-72 when using APRS.
I did some ground testing today and with the transmiter on the ground. I needed to be within .2 mile to reaquire the signal.
Same distance I ran into with my 900mhz unit.
I was thinking about getting a mag base antenna for the D-72, but I have one for my 900mhz unit and it did not help much.
So my question is what is a good mobile antenna set up for the Kenwood D-72 on 70cm in APRS mode once the transmitter is on the ground?
Once the transmiter is on the ground does the antenna set up help much?

 

[SteveF]

I have a nagoya NA772 antenna that I can try once I get the big red bee unit some time this week - says he is shipping it tuesday - it is about 15" long and claims 3db on 430 - but doesnt say compared to what - so typical on antennas -

 

[n5wd]

Once the transmiter is on the ground does the antenna set up help much?

Yes, and no. VHF communications (say 30MHz to about 300 MHz) are said to be line-of-sight plus a little bit. That is, if you can "see" the transmitter, then you should be able to hear the transmitter, plus a little bit of distance extra.

For UHF, 300 MHz and up, which includes both the 430 MHz of the normal BeeLine GPS and the 900 MHz that you're playing around with, it's strictly line-of-sight, with little or no wave refraction around objects. That means you HAVE to see the transmitter in order to hear it.

Once you're on the ground, if you can't "see" the transmitter, then you're not going to be able to hear it. But, with a higher gain antenna, which is able to be pointed in a particular direction and focus all of the antenna's power in that direction, you will be able to determine the direction the signal is coming from. Thus a short yagi (3 or 4 elements) will be better all-round than the omni-directional mag mount antenna you're using, once you get physically close enough to hear the signal.

That make sense?

I have an Arrow antenna ( https://www.arrowantennas.com/arrowii/146-437.html ) that I originally got before I got started back in rocketry. I used it to talk through satellites when we went on vacation. It's highly portable and covers both the 2m and 430-450 MHz ham bands. The link, above, will show it to you. For rocketry, I can just use the back 3 elements of the antenna (it breaks apart in half, and I just don't hook up the 2m elements) and I've got a very portable moderate gain antenna for use in direction finding. You can easily make one of these yourself using the designs by Kent Britain, WA5VJB, one of our local antenna experts. See this link for some of his "cheap yagi's" made out of wood and welding rod. Make your own for about $10.

https://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf

 

[mIcahel]

Went the cheap/home made route for my 430 setup with
parts from radioshack, local hobby store, and salvage from some
fancy crutches I had in the garage. Knew there was some reason I
saved those fancy crutches.

 

[JimJarvis50]

Jim, I was having the same thoughts as you (too scared to rely on a yagi with the gps in case I had no idea where to search), and tried out your idea with the 8GR mounted on the yagi and both beeline TX and GPS coming into the unit. It seemed to work well, I only found one real issue (for me)...

At 16 miles, with 7 element yagi and VX-8GR, there was a very narrow window for decoding the GPS packets (more or less had to have the yagi pointed directly at the transmitter). However, the TX signal was still very strong, and even with maximum squelch there was probably a 90 degree window (vertical and horizontal) at which the signal could be received. So its not really directional enough to be of great assistance in finding the GPS transmissions.

I added a arrow antennas 4Mhz offset attenuator into the setup, but apparently even just adding the unit into the circuit creates enough attenuation to kill of any signal from both transmitters. So scratch that idea.

Does anyone have any ideas regarding the above....hopefully it makes some sense.

John, do you have the link/part number for the USB cable?

Regards
Ethan

Ethan, I didn't see your post. Sorry to be so slow responding.

I'm still practicing with my setup, so I don't know all of the ins and outs yet. However, my experience with the attenuator is that it doesn't affect the normal signal, only the shifted one. Best as I can tell, the gps (on B) is not attenuated, nor is the tracker signal (on A) at the normal frequency.

I tried the attenuator on the radio (10 dB) and it does nothing to sufficienty attenuate the beeline tracker.

Here's my setup.

https://www.flickr.com/photos/11803405@N08/5501325774/

Jim

 

[Ethan]

Hi Jim,

Thanks for getting back to me. What I found was at 15 miles out, just having the arrow antennas offset attenuator in the circuit added enough attenuation to kill of any signal from both transmitters. When I removed the unit from the radio I got a nice strong signal from both once again.

I'm still trying to figure out whether it's user error or unavoidable. I hope to get back to testing soon.

Ethan

 

[JimJarvis50]

Hi Jim,

Thanks for getting back to me. What I found was at 15 miles out, just having the arrow antennas offset attenuator in the circuit added enough attenuation to kill of any signal from both transmitters. When I removed the unit from the radio I got a nice strong signal from both once again.

I'm still trying to figure out whether it's user error or unavoidable. I hope to get back to testing soon.

Ethan

Interesting. I did some testing where I went to the edge of where I could still hear the beeline transmitter. Then, I tested with and without the attenuator and found no difference. Oh well, it will either work or it won't. As you pointed out, without the attenuator, the beeline doesn't provide the directional signal needed for tracking or pointing the antenna for the gps.

I'll get another shot at it tomorrow.

Jim

 

[Ethan]

Cool, thanks Jim. So I know its a bug in my setup somewhere...possibly a damaged attenuator. I'll look at it closer when the weather plays ball again.

Regards
Ethan

 

[troj]

Ethan...

What are you using for cables? Are they possibly longer than is necessary? Are you using adapters, or do the cables themselves have the right ends?

Use cables that are no longer than absolutely necessary, and try removing adapters from the setup, and see if that helps.

-Kevin