Servers by jDrones

Boosting 3dr radio


(product78) #1

I was wondering if any of you have had success boosting the strength of your 3dr radio’s signal.
bidirectional antenna?
omni?


(Bill Bonney) #2

Most people look at buying a RFD900 for more power.


(product78) #3

I also looked at the rfd900. I believe it’s over $100, though. So, if it is possible to boost a 3dr signal with a 10 dollar investment in an omni or bidirectional antenna, why not.
By the way, I also came across a couple 3dr mav link models that are worth looking into.

  1. a 500mw 3dr radio telem (most 3dr radio mavlinks are 100mw or less)
  2. a dual ttl 3dr radio telem (not sure if there is an added benefit w/ this model)

(Andre-K) #4

3DR does not sell any "500"mW radio, Hobbyking does, they sell "500"mW radio , that is, maybe at best 150mW judging by my results.
I did test that with proper antennas, compared to standard 3DR radios.
that is not worth the price and connector mess.
good antennas and as little rf noise onboard as possible is the best solution.


(product78) #5

Andre-K
thanks for the input. You mentioned that you tested the 3dr modules with the “proper antennas”. Which antennas, specifically did you test them with.
Anyone that reads the product description of the rfd900 is going to see that it clearly has superior telemetry specs to the 3dr radio. But if you can get the current 3dr radio to boost it’s signal enough to give you 2 or 3 km of range, then at least for my purposes, their is no need for the rfd900 or a cellular tele unit like drone cell.

Even the rfd900 documentation references it’s variation in range depending on which type of antenna is used.
(below, an excerpt from the rf900 product description)
Long range >40km depending on antennas and GCS setup *80km demonstrated by Edge Research labs on a balloon !, 57km in India, on Dipoles.
2 x RP-SMA RF connectors, diversity switched.

You may notice that they reference the long range of >40km in the description, "depending on antennas"
But they never give the figures for range with specific antenna applications.

Is anyone here familiar with this information about specific antenna performance & range data?
Can anyone here speak to how well the rfd900 works with apm planner 2.0 or mission planner, tower?

regarding the 500mw 3dr radio that I mentioned. It does appear to be manufactured by a 3dr clone company called HopeRF It claims to give you 2.5 km of telemetry range. That is approximately 5x the range of the current 3dr radios that so many of us use;

ebay.com/itm/2500M-3DR-Radio … 2ee67a7b58
listing can be viewed at
ebay.com/itm/2500M-3DR-Radio … 2ee67a7b58

below are features of the unit:
6-position Molex connector
• 500 mW maximum output power (adjustable)
• -117 dBm receive sensitivity
• SMA connector
• 2-way full-duplex communication through adaptive TDM
• UART interface
• Transparent serial link
• MAVLink protocol framing
• Frequency Hopping Spread Spectrum (FHSS)
• Configurable duty cycle
• Error correction corrects up to 25% of bit errors
• Open-source SIK firmware
• Configurable through *Mission Planner and *APM Planner
Specs:
Supply voltage: 3.7-6 VDC (from USB or Molex connector)
Transmit current: 500 mA at 27 dBm
Receive current: 25 mA
Serial interface: 3.3 V UART
Included
• Two radio modules with antennas
• Android USB/OTG adapter cable
• 6-wire Pixhawk connector cable
• 6-to-5-position APM and PX4 connector cable


(Bill Bonney) #6

HopeRF make the radio module hoperf.com/rf/data_link_module/HM-TRP.htm

The firmware is OpenSource from here github.com/Dronecode/SiK

I don’t see HopeRF making a 500mW unit.So i would question if that is available. Especially since the picture shown show in the link you give shows no extra components that could be considered as a linear amp for the signal.


(Andre-K) #7

like billbonney said, HM-TRP is 100mW , I did not check, but I guess HK or subvendor just drives something out of specs , maybe just providing too high voltage. the module. - there are no extra power stage in the HK module, the HM-TRP (if original) is connected to SMA

below is a comparsion between 3DR and HK radios, one with RMILEC antenna, and the other with a 14db Comtelco Yagi. over 4Km. (tested across a fjord, ground-ground)
Of course, little to no local noise, and no USB noise. all is 433Mhz. The cells are a mess, but then you dont have the complete spreadsheet (I don’t really share this resaearch, and test much more than this.)

If you are serious about this, and I assume you live a place where 900Mhz is legal, check out P900 from microhardcorp .

	RSSI  dBm		Noise dBm		SNR	
	Local	Rem.	Local	Rem.	Local	Rem.

HK500mW HK500mW -68.5789473684 -67.5263157895 -101.7368421053 -114.3684210526 33.1578947368 46.8421052632
3DRV2 3DRV2 -69.6315789474 -74.8947368421 -105.9473684211 -111.2105263158 36.3157894737 42.3157894737


(Flyhard) #8

That about a direction patch antenna on the receiver? Works like a charm for long range video links, so I suspect the same here.

Sent from my iPhone using Tapatalk


(Bill Bonney) #9

Better antennas will mean better reception due to noise rejection. Using directional antennas will improve range limits for sure. It’s much better to improve rnage with antenna, that power in the first instance. More power always comes with more noise from the radio, so can be even worse with a poor quality antenna.


(product78) #10

I wrote the vendor of the listing that I linked in previous post to ask about the featured specs in his item listing. Below is what I wrote to him and I’ll update if I get a reply.

Your listing has been the subject of debate on the ardupilot forums. More than one forum member has expressed their doubts in the validity of the specs that you have listed in your item description.
a link to the topic in the ardupilot forum called, “boosting 3dr radios”;
viewtopic.php?f=64&t=13902

The spec that is under question is the claim of 500mw and the 2500m range. Can you back these claims up with documentation from HopeRF?

I should mention that I noticed listings for 500mw 3dr radios are now popping up left and right on ebay. And not just the hope RF radios. There is a model called X-rock telemetry v3 and cuav 3dr radio. Both claiming 500mw power and 2.5km range.


(Bill Bonney) #11

You can get 2.5k with the 100mW version.

I look forward to hear the response.


(product78) #12

The ebay seller who posted the listing got back to me within 24 hours. I’ll post his response below;

Dear massivedynamic78,

That’s a great question. I don’t have any official documents as of yet. The vendor I purchased this item from is on vacation for a few more days.

Unfortunately, I don’t have a RF meter or network analyzer and I have no way to really know.

If you give me a few days, I could open a package and do a range test. It would be good to know the range.

I couldn’t find 2500 meters in my eBay ad. Could you tell me where in my ad that you’ve seen this?

Unfortunately, this does not yet settle the issue. But credit to the ebay seller for replying in a steadfast manner. I think he is likely on the level and I expect he wants to get to the bottom of this as much as me. I’ll continue to make updates as I acquire more info on the topic and greatly appreciate anyone who cares to share their 411.


(product78) #13

I got another response from the ebay seller who listed a 3dr radio as 500mw

New message from: ftadepot (337Turquoise Star)
Okay. Thanks for pointing that out. It’s funny because I somehow missed that. I seen other guys selling the 500 mW radios and selected “sell one like this” from eBay. So it categorizes accordingly. I’ll remove that soon and do a range test. I will get back with you on the numbers.

Thanks for all the input

On 10/8/15, 1:20 PM, massivedynamic78 wrote:

Re: Details about item: massivedynamic78 sent a message about 2500M 3DR Radio Telemetry 500mw 915MHZ LONG-RANGE TELEMETRY for APM or Pixhawk #201435282264

listing says “2500m 3dr radio”. I assumed 2500m stood for 2500 meter


(product78) #14

bill bonney said,
“you can get 2.5 km with the 100mw 3dr”

I imagine you could with upgraded antennas, but I have never gotten more than 8 or 900 meters of range, reliably.


(Rjiun RK) #15

Can anyone suggest me a long range communication method to my arduplane?