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Old Apr 14, 2011, 11:42 AM
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arocholl's Avatar
Spain, Community of Madrid, Madrid
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Originally Posted by jalves View Post
And if we can change the central frequency (but continue with a 9000 freq span) in order to use for instance 434~444MHz sweep ?

This would allow me to check all the frequencies covered by my LRS (TLRS).
I see your point, didn't know there was a 434-444Mhz LRS out there. I will see what options are available for doing that. However, you should account for about 5dBm degraded sensitivity in the 440-444Mhz range. Would that be ok?
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Old Apr 14, 2011, 12:03 PM
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jalves's Avatar
Portugal
Joined Mar 2004
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430-444MHz would be super,

But if I can select a centre frequency with the allowed freq. span and then sweep up and down from 430 till 444MHz , this would be the cherry above the cake.
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Old Apr 15, 2011, 10:46 PM
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USA, IN, Bloomington
Joined Aug 2007
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spikes

Does anyone have any idea what is causing these spikes? They seem to be fairly constant and not really dependent on where I am in my house. They don't go away if I put the unit in the microwave (no I didn't turn the microwave on).

We don't have any alarms that are wireless. Our wifi is 2.4 and our phone is 5.8. Could it be cellphones?

Edit: problem solved by upgrading to new firmware. See post below.
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Last edited by BloomingtonFPV; Apr 19, 2011 at 03:26 PM. Reason: problem solved
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Old Apr 15, 2011, 10:49 PM
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Charles Town, WV
Joined Jan 2008
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Try driving it to a new location and checking?
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Old Apr 16, 2011, 04:10 AM
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Spain, Community of Madrid, Madrid
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Originally Posted by BloomingtonFPV View Post
Does anyone have any idea what is causing these spikes? They seem to be fairly constant and not really dependent on where I am in my house. They don't go away if I put the unit in the microwave (no I didn't turn the microwave on).

We don't have any alarms that are wireless. Our wifi is 2.4 and our phone is 5.8. Could it be cellphones?
Can you tell me what you get if you remove the antenna completely?
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Old Apr 16, 2011, 06:26 AM
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If I remove the antenna the signal drops from -85 db to about -91.

I tightened up the screws on the unit (they seemed a little loose), and the signal peak with the antenna on is now at about -98. If I take the antenna off it drops to about -103.
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Old Apr 16, 2011, 06:49 AM
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Spain, Community of Madrid, Madrid
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Quote:
Originally Posted by BloomingtonFPV View Post
If I remove the antenna the signal drops from -85 db to about -91.

I tightened up the screws on the unit (they seemed a little loose), and the signal peak with the antenna on is now at about -98. If I take the antenna off it drops to about -103.
Thanks, that makes sense. That is electrical background noise, it should be about -105dBm, now with -103 you get closer to that. The only explanation I could give you is probably you are in an environment with either very high humidity, or extremely low humidity with static electricity around.

The good news is I improved the background noise averaging significantly more in v1.06 Beta 01, if you are willing to upgrade your unit we can easily confirm that. It takes 5 minutes and you should get your background noise at least in the -110dBm region after the upgrade.
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Old Apr 16, 2011, 07:44 AM
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Ok, upgrading to 1.06 worked and the spikes are no longer visible.

I like the new display.

Thanks for your help with this.
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Old Apr 16, 2011, 08:35 AM
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Originally Posted by BloomingtonFPV View Post
Ok, upgrading to 1.06 worked and the spikes are no longer visible.

I like the new display.

Thanks for your help with this.
Excellent, thanks.
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Old Apr 18, 2011, 05:03 PM
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France, Pyrénées Orientales
Joined Feb 2009
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Hello

you know when version 868 Mhz will be available ?

I use DMD LRS 868Mhz

thank's for support

jdm66
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Old Apr 19, 2011, 03:27 AM
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Spain, Community of Madrid, Madrid
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Hello

you know when version 868 Mhz will be available ?

I use DMD LRS 868Mhz

thank's for support

jdm66
Hi, thanks for your interest.

We are working in next production batch, but I don't have a confirmed date yet. Based on international stock availability, I guess it will take a couple of months to be available - that means mid or end of June most likely.

Regards
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Old Apr 19, 2011, 07:23 AM
ysb
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quebec
Joined Dec 2010
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I just bought one for my 433 mhz LRS system (Chainlink LRS ) but do you have any new about "module" for 2.4 / 5.8 Ghz ? (5.8 will be great to check for FPV Video tx)
and a stupid question : can we use the RF explorer as a "SWR meter" in some sort to adjust our Aerial ? (perhaps with a special firmware ? it's so versatil...)
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Last edited by ysb; Apr 19, 2011 at 07:28 AM.
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Old Apr 19, 2011, 01:10 PM
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Originally Posted by ysb View Post
I just bought one for my 433 mhz LRS system (Chainlink LRS ) but do you have any new about "module" for 2.4 / 5.8 Ghz ? (5.8 will be great to check for FPV Video tx)
and a stupid question : can we use the RF explorer as a "SWR meter" in some sort to adjust our Aerial ? (perhaps with a special firmware ? it's so versatil...)
Hi, yes we keep working on 2.4Ghz module, first bare boards have been produced already and we expect to have Beta modules available in May. 5Ghz modules are planned at some point after summer, no clear date yet.

As per VSWR meter, you need an external directional coupler, and RF generator and a spectrum analyzer. See some description here and here.

It can be done with two RF Explorers, one as a RF Generator and the other as Spectrum Analyzer, we may produce some instructions in the future as part of growing list of RF tutorials we have planned. However, VSWR is just a minor part of antenna design. As a friend says, a 50ohm dummy load has a perfect VSWR but that doesn't make it a good antenna, quite the opposite. VSWR analog meters are very popular because they are cheap for HAM radio bands, but you use them mostly when you cannot afford a spectrum analyzer and do field test. This shouldn't be a problem now you own a RF Explorer.

This is what I suggest you to do to improve your antenna: get a male SMA connector and solder a cable wire to it. Start with a cable length larger than 17cm which is 1/4 wave for 433Mhz. Start for instance with 20cm. Put your RF Explorer at a specific distance from the LRS transmitter longer than 10 wavelengths (10mts would be ok). Then using average calculator in the RF Explorer, try out shorter cable lengths till you get the best possible dBm. Regardless VSWR, that will be the best possible antenna for this frequency assuming a 50ohm load. The beauty of a spectrum analyzer is it takes into account everything (including insertion loss), not only VSWR, and gives you a simple read of how efficient your antenna is for a given distance, orientation and frequency.

If you can use a 3/4 wave or even longer, try that, you can get up to 6dB more in many cases. Remember orientation is important, as all real antennae are directional. So try to imitate the most likely orientation your plane will have with the transmitter on land.
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Old Apr 20, 2011, 08:20 AM
ysb
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thanks for your answer, i will try that
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Old Apr 20, 2011, 10:44 AM
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I've used the directional coupler approach and it seems to work fine, although I'm looking forward to using the 2.4ghz addon which should work better. The directional couplers are only like $25 on ebay and the diodes are cheap (I have a few extras if people need them).
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