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Author Topic: Negatives to using a cheap SDR radio with an amplifier?  (Read 5503 times)
ZENKI
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Posts: 1424




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« Reply #15 on: September 15, 2017, 06:18:51 PM »

The QRP limit is a  contest rule not a  rule that has to be enforced generally who cares if its 5 10 15 or 20 watts its low power.

We should design the tranceivers output  power to radiate enough power to complete a HF circuit. It can easily be modelled in VOA CAP using simple antennas like dipoles or verticals.

We  should change this "QRP" Mentality from  QRP 5 watts to something like "Minimum Necessary communications  power" HF is no different to EME, depending on the path it requires a minimum of antenna gain, radiated at angle X with power X depending on mode. That should determine the  QRP rules of engagement rather than some ridiculous arbitrarily chosen power like 5 watts. If you still stubborn and want to try EME with 5 watts you can do what you want. But please use a technical  analysis to make a decision about   QRP power rather than the emotional delinquent arguments QRP advocates drag up to justify 5 watts.

My preferred QRP power level is 20 to 25 watts because I mainly use Mil Manpack HF radio. The military incidentally chose this power level because it was considered to be effective to get the message through and the job done without banging your head against a brick wall screaming your lungs out. It was  also the best power for effectiveness versus battery technology and life.

Most QRP operators who buy these 5 and 10 watt radios eventually end up buying a crap 50 to 100 watt CB amplifier and cause a lot of splatter. They also now have to carry a big bag of crap in the trunk to use this complicated setup of batteries cables and amplifiers. The KX3  is an example of bolt together mess  of junk and cables. If these same manufacturers designed these radios with 20 to 30 watt  PA's whose power can be reduced more operators could have more effective fun. A KX3, FT817 or  many of the other  10 watt QRP radios can easily be designed with a   high efficiency 30 watt PA and the size would be close to the same size. These days with 18650 batteries being used everywhere even in Tesla cars you could run this radio for longer than a 5 watt useless Dick Tracy watch radio that cant be heard. So many hams are emotional suckers for punishments because they believe god made the 5 watt QRP radio rule, they still have not figured out its about completing  and passing the message IE communicating rather than being obsessed about trying to defeat the laws of physics.

I am not saying that 5 watts does not work. But  QRP is like giving a cell phone to a kid with no internet enabled connection and say try making contacts. Its a sure way of discouraging people away from ham radio. If we gave new QRP hams or new start hams  25 to 30 watt radios even with   average to poor antennas and even bits of wire they could have much more fun that  trying the same trick with 5 watts.




SoftRock RXTX  
Peaberry SDR V2

For $90 to $150 I could get on the HF bands with most modes. The only downside is these radios only put out about 1 watt to 2 watts of power.

Would there be a downside to getting started with one of these, then later getting a linear amplifer to push these to more usable power? Or would it be a better idea to save for a bit and get a nice radio that can do all modes, and be able to put out 100 watts?

I know it's not super easy to say for sure which would be better, but I wanted opinions on what you would do in my situation.

It IS super easy to say for sure that newbie Hams that buy QRP HF Radios get frustrated and leave the hobby. If this is your goal then have at it. QRP HF Radios are for experienced hams that know what they are getting into, especially since HF propagation is headed for the toilet.

OTOH if as a newbie clueless Ham, you WANT to be successful, then get a job,  (or better yet) get a job for your wife and buy a real 100 watt radio with a good or great antenna. You will end up being a ham for life...  Wink

Stan K9IUQ
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ZENKI
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Posts: 1424




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« Reply #16 on: September 15, 2017, 06:27:25 PM »

Exactly why would anyone want to buy a old piece of crap from 70's and 80s that does not even match the performance of a radio like the TS590S or even the IC7300. Whats worst is that these old pieces of junk are selling for prices close to what they sold for back then or slightly less. These radios have crap receivers, crap transmitters and lack performance. Why should any ham   have to put up with drifting 100hz tuning radios with no performance when you can buy a radio like the TS590S  or IC7300.

Thats before we start talking about the tube junk that is so glorified. Then lets talk  about the non availability of spare parts. The second ham radio industry is the only electronics industry where old electronic junk can be sold for stupid prices. Most radios from the 70's and 80s should be selling from 100 to 200 dollars not the 400 to 700 dollar prices that I see them sell for.

Worst still is the new trend in EX CB hams buying and collecting crap junk CB radios and selling them to equally stupid EX CB'er hams for ridiculous prices. Hams paying stupid prices for 10 dollar CB radios. The stupidity is palpable. It would not be so so bad if these radios had decent receiver or other receiver specifications but they are cheap  junk that were manufactured in sweat shops not in NASA quality labs!

Buy a TS590SG and be done with it.

Get an old radio to start with, like a ts440 or Icom 735.

This is horrible advice. Buy an overpriced outdated lame HF radio from the 1980's that the oldtimers have tried to dump for YEARS. C'mon, I have seen modern competitive used radios like the Kenwood TS-590s in the $700 range. No need to buy junk like a TS-440 that smells like a dirty ashtray and with likely PLL  ..... problems.  Cheesy

Stan K9IUQ


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VA3VF
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Posts: 817




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« Reply #17 on: September 15, 2017, 06:28:29 PM »

The QRP limit is a  contest rule not a  rule that has to be enforced generally who cares if its 5 10 15 or 20 watts its low power.


QRP limit is not a contest rule, it's a very interesting aspect of the hobby, as is milli/microwatting. Contest rules use the same power level, but they were not the 'trend setter'. For more info, read the story of the QRP ARCI.

In any case, the opening question was about two SDRs that have 1 and 2W out respectively.
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ZENKI
Member

Posts: 1424




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« Reply #18 on: September 15, 2017, 06:32:38 PM »

This is very good  advice. There is a massive ham radio recycling industry  led by hams who are ham radio parasite sharks who are mainly ripping off newcomers to the ham radio hobby. They are using charm and marketing hype reselling crap to these new hams for prices that are close to the new 1980's prices or even more. They like peddling the fact that this stuff is good and a good investment. Its utter rubbish that no ham should be buying.  You can see that even ham radio dealers want to get into the act because they make more margin selling old hyped up crap than new radios that work better. You can look for these dealers who are looking for estate and old ham radio equipment as tradeins etc. Stay away, smelly, design problems, no parts and mostly glorified junk.

Very good advice from K9IUQ

If you need a great radio, or even a good radio to have fun operating, then I have not had fun most of my operating years.
After about 30 years I did manage to get some nice modern radios, and they tend to be the LEAST amount of fun...
I still have and use my old home brew stuff but nothing modern has lasted a year in my shack.
Most does not last 3 months.


I have and use both Vintage radios AND modern stuff - see my QRZ.com page.

I would NEVER recommend a radio from the 80's to a newbie HF ham. The new technology is just too good on later model radios. Plus the old radios are too limiting when used with a Computer. Plus you recommended a TS-440s, a radio that is known for problems. Problems that a new ham should not have to deal with.

A newbie ham can not have fun in ham radio with a junker Radio that frustrates a new ham. I have seen too many new Hams leave the hobby because of frustration...

I equate Old vintage cars with old radios. They ARE fun to drive once in a while and show off to your buddies. But you want a modern car/radio for everyday driving....  Cheesy Cheesy

FWIW I have been a Ham for 57 years and love the new radios and new technology like SDR, digital modes, Fusion,DMR, FT-8 and the list goes on Never Bored yet.

Stan K9IUQ




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ZENKI
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Posts: 1424




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« Reply #19 on: September 15, 2017, 06:38:37 PM »

I am not denying that there is  an interest in low power   or QRP on all modes and bands.

I am specifically talking about the  the HF QRP 5 watt contest  rule limit that is not even mode dependent. Theory would suggest that 5 watt CW is  more effective than SSB, so in theory  if the limit is 5 watt CW the equivalent effective power output on SSB should be double or   even 4 times the  CW output power to maintain the same SNR.  Determining the power living as an arbitrary figure as in the contest HF power limit is  technically flawed.  That is not to say that if you have effective antennas or a location that can propagate such  low power levels   that you should not try and experiment or use such powers. We need more science in in the arguments for determining power levels  based on  mode and frequency.

The QRP limit is a  contest rule not a  rule that has to be enforced generally who cares if its 5 10 15 or 20 watts its low power.


QRP limit is not a contest rule, it's a very interesting aspect of the hobby, as is milli/microwatting. Contest rules use the same power level, but they were not the 'trend setter'. For more info, read the story of the QRP ARCI.

In any case, the opening question was about two SDRs that have 1 and 2W out respectively.
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VA3VF
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Posts: 817




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« Reply #20 on: September 15, 2017, 06:51:03 PM »

We need more science in in the arguments for determining power levels  based on  mode and frequency.

I'm going by the history of QRP, which is also available in books authored by Ade Weiss. There was no science in picking 5W. In the days of the WQF (World QRP Federation) of the late 70 early 80's, QRP phone had a higher output 'allowance'. To simplify things, the same 5W power became the accepted 'standard' for all modes. Later on, QRPp (<1W) and QRPpp (microwatts) were introduced for the pleasure of the 'masochists' (just kidding). Again no science. The closest it got to science was comparing a 59+30 signal reading at 100W, and decreasing as per signal level standards, to show the theoretical possibilities of QRP. 
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K6BRN
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Posts: 459




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« Reply #21 on: September 18, 2017, 10:12:20 PM »

Zenki:

You're showing a major lack of judgement and design experience in saying:

Quote
its very easy to design a 500 watt to 1 kilowatt amplifier that can easily be driven by  a signal generator.

Or you're just exaggerating the case way too much.

Do you REALLY think its as easy to design, develop and reliably produce a cost-effective amplifier with a gain of 60 db as it is to produce one with a gain of 15 db?

Surprising, since you are the self-proclaimed champion of signal purity and stability.

You seem to have forgotten about isolation, and how the cost of design and production rises dramatically as isolation between stages rises with them. Unless you ignore stability and signal purity.  Bing!  Bang!  Boom!  Screech!

Perhaps price is not part of your calculations.

Much better in the general case to break the signal chain into two parts, with a robust signal level between the two,  and let the buyer chose the cost they are willing to bear.

Brian - K6BRN
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LA9XNA
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Posts: 188




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« Reply #22 on: September 18, 2017, 10:23:55 PM »

Welcome to the hobby!
If you need a start up rig, contact the local hamradio group and ask if there is anybody in the group that got a used radio for sale with a price within your range.
A lot of the groups got a mailing list that might be the way to ask if anybody got a rig for sale.

If you thinking of building something eBay might be a good place to start.
you can find PA kits and transceiver kits for a decent price.
Remember that a singel band radio usually is a simpler and more robust construction than a multi band.
A decent monoband rig to start a build is the BITX it is normally a 20m or 40m qrp range rig, but can come in other variations as well.
Be observant of the shipping price, some of the sellers on ebay will rip you off on the freight.
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NI0Z
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Posts: 683


WWW

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« Reply #23 on: September 20, 2017, 02:54:04 PM »

Welcome to the hobby!
If you need a start up rig, contact the local hamradio group and ask if there is anybody in the group that got a used radio for sale with a price within your range.
A lot of the groups got a mailing list that might be the way to ask if anybody got a rig for sale.

If you thinking of building something eBay might be a good place to start.
you can find PA kits and transceiver kits for a decent price.
Remember that a singel band radio usually is a simpler and more robust construction than a multi band.
A decent monoband rig to start a build is the BITX it is normally a 20m or 40m qrp range rig, but can come in other variations as well.
Be observant of the shipping price, some of the sellers on ebay will rip you off on the freight.

This is probably best advice I have seen so far, a club me,beer might even have a rig they would loan you to get started or even have a loaner you can checkout and use.

Your doing well to ask!

QTH.com classified adds is also a decent place to find used gear if you really want to go that route.  Genesis used to have SDR kits as well, however, I don't know where they stand today, you'd have to check.

73
NI0Z
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W8KFJ
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Posts: 55




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« Reply #24 on: September 28, 2017, 01:21:25 PM »

KI7LGC - Congrats on the general!  The HF bands will open up a whole new world.  You mentioned a couple of really cheap SDRs.  I built a Peaberry V1, and made a number of SSB contacts all over the eastern US with 1 watt, then added an amp.  You can do a lot without much power!

I am definitely an SDR convert.  You need to do your homework.  If your limit is around $500 or so, find a good bargain in a used 100 watt traditional superhet radio.  There has already been some excellent advice about that.  You can always get your money back.

If you can spend around $1000, many better options appear.  Today, I would only buy a DIRECT-SAMPLING SDR.  While many have voiced their concerns about a 5 watt rig, I am beginning to see that as the preferred configuration.  They can be small and light, perfect for portable use.  Add any kind of amplifier you choose.  I have a Hardrock 50 ($300 kit), as well as an Ameritron ALS600 (600 watt solid state amp) which I have modified to run full output driven by my 5 watt Elad FDM-DUO.  Small rigs are easy to ship too - in case they need fixin'.

Check out my QRZ page.  There are some SDR articles, and some videos on the use of the DUO.  Then look elsewhere for more research.  Enjoy your new privileges!

Dave  W8KFJ
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KC8MWG
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Posts: 445




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« Reply #25 on: November 10, 2017, 09:56:40 AM »

At the risk of getting flamed, I will freely admit to using a linear amp with my QRP rigs. I have both a kit-built mcHF SDR (v. 0.6) and a Yaesu FT-817ND. I use a Chinese MX-P50M 45 watt amp, which, despite the folks that like to deride Chinese electronics, works well and puts out a clean signal (review here: http://gm4slv-geek.blogspot.co.uk/2015/03/mx-p50m-amplifier-for-ft817.html ). I save the low power level for digital modes, and use the amp when conditions are less than stellar. The MX-P50M is available for less than $200. There is another variation called the MiniPA-50 which features automatic bandswitching when used with the FT-817, and which I am considering trying out.
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