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Discussion in 'CB and Export Equipment and Accessories' started by mag69, Nov 16, 2005.
Would the SP1A be worth the install on a Uniden (president) Grant?
If you talk on SSB a lot sure! If you just use it for AM maybe not as much! I am on SSB 3X as much as AM so for me it makes perfect sense. You can use compression on AM but not as much and it makes slightly less of an impact. That said I know plenty of people that use them on AM and I am not trying to talk you out of it just pointing out my bias. In fact the first time I heard one back in 1991 was on AM!
If you are mostly on AM splitting the difference between Goldfinger Mod and the stock component values and a recap and adding an SL41 mic might be more useful.
What is the Goldfinger mod?
Replacing certain caps in your radio to widen your tx or rx
My old Uniden is mostly used on sideband, so I think I'll give the SP1A a shot and see what the locals say. They are honest with me and will let me know when my radios sound good or bad.
What happened to the guys who build them from scratch instead of buying over the counter stuff?
Goldfinger is a guys handle and he posted a hifi mod a long time ago. He goes a bit too extreme though and puts such large caps in that you get far too much bass and not enough hi freq.
Ideally you want to select caps in the audio chain not just by going with larger values but some larger some small to shape the filtering, You could never walk someone through that process though and they would need some test equipment to do it right. In a perfect world the person doing it would be the owner so he would be talking into the mic as he made cap substitutions. Ideally a decade box aka substitution box would be used to speed this all up. I sound like Darth Vader so the last thing I need is huge increase in bass. I normally have to down size a few caps early in the audio chain and than increase them further down but I have never gone extreme like Goldfinger. In keep lytics in chain but will sub ceramics out for film caps. If I just can not get the audio smooth I will make composite caps where I have lytics and small value film caps combined to smooth things out. If you put too much bass in you will ruin SSB entirely and you will not get well on AM. You will sound fantastic which is fine for local rag chewing but forget about DXing like that!
When you do this sort of thing you usually need to mod the amc a bit too to really get all you can out of it.
Unfortunately in the Goldfinger mod if you do not have test gear you can end up with some seriously messed up audio and mod wave form. That is the problem with doing predetermined mods from someone else with out the ability to see what is going on it is like a shot in the dark. I like his recieve mod even less but it is a place to start and to learn and tinker with if you have the desire.
I have done some of his mod's and normally I end up with 1/3-1/2 the value he recomends. For instance in one radio the stock cap is .22uf and he wants you to put a 1uf film cap in. In another spot I think he calls for a 2uf film cap but the stock cap is a tiny ceramic that I think is maybe .40uf.
It does no good to do all this work either if you have a stock mic on the radio you need a mic that has more bandwidth and it also has to have nice tight clean audio bandwidth is no good if it is muddy sounding.
He is kind enough to post his mods for a variety of radio's so even if it is not the best mod it is free and you can use it to learn a lot.
Any radio over 15 years old always get's a complete recap when I own it especially if it is new to me and I do not know it's history. If it is NOS especially since nothing kills a radio like sitting on a shelf not being used! In old radio's that have poor audio, poor receive or are acting goofy I do not do anything else until I completely recap it. Newer radio's have a lot fewer caps in the design.
Digital is what happened. Have you seen the current HF rigs?
On the buying pre made why don't you make your own mic cartridges like Heil did? Because it is time consuming, not that rewarding, way too expensive and frustrating to roll your own.
Why do we not make out own capacitors?
I made my own switching power supply in college with ARRL plans in the back of my ARRL Handbook. It had mistakes in the printing and it was a real pain compared to buying a switching supply. I would never do that again unless I had no other option. I can buy better thought out, more efficient and cost effective off the shelf product.
Now as a hobby it makes perfect sense especially if you use it as a learning exercise or to eat excess time.
I think people look at it like this. If it affordable and of sufficient quality in both design, parts and execution they would rather buy. If the price becomes unreasonable, parts quality is lacking or the execution is poor they would rather build it them selves.
I think people also have to be passionate about what they are doing. I have 200Mhz scope, and signal generator, and a lot of other gear but electronics and tinkering with electronics is a not my favorite hobby if I had sufficient quality technician in my area I would not bother.That said I have a lot of gear and if I had to pay someone to work on it all I would need a second mortgage. LOL The current state of affairs has made it necessary for me to get new gear and learn to use it at a higher level of proficiency because there are no good electronic repair shops any more in most area's.
I also do not want to give the post office any more opportunities than I have to to ruin or lose my stuff!
Even when you look at the Amateur Radio Operators with an online presence that do design and build their own gear often they use Chinese made modals in their designs. One wrote a nice article on building Mosfet RF Amplifiers and he used a Chinese made boost transformer in his design instead of building one himself! He could not build a 12V to 30V 4amp boost transformer with IC control as cheaply as he could buy on off ebay!
I did not look closely at what you put up schematic wise but I am betting it uses an obsolete opamp or audio ic. A lot of free designs online use parts that are obsolete and hard to find with no direct sup. When that happens you need to be able to read a data sheet and rework a design and change components to match the new audio IC or opamp! So that would mean specialized knowledge not paint by number's! Most data sheets give an example circuit often as well.
I was thinking as I was reading your post a Cap sub box. You were thinking the same thing. would work perfect. Even listening on a monitor radio I just can not get a real good clear sound of the radio I am working on. Possibly I am tone deff.? Makes me think that is why I am not a great musician. LOL
Codeman Please keep us posted after the install.
The sad part about the op amp idea is the "Split rail" power supply requirement for true analog processing - although ok and seems to work well, there are problems in that design versus running analog and single ended power supply rails using discretes.
You can break down an amp into the discrete function and "Tailor" it's response and it's easier to install into something that already is doing it that way.
The hardest part is to obtain the input signal with the best possible means of capture for reproduction - some like FET styles but aren't exactly linear - act more like Crystal resonation - "kinda crunchy" if not done right.
Others are like dynamic, vibrate a membrane to get the coil to move in the field and a smooth wave - albeit small is generated - capturing the best fidelity with the least amount of Emphasis - welcome to RIAA phono input from the 70's turntables.
Get the right membrane mounting and coil pickup design - any class A amp will do - to a certain point.
- CB's do that already - the "split rail" (pull up or down or float) in biasing as needed. The problem lies in the linearity of the amplifier - not just the "oomph" (work with me here) So filtering and throwing in a better-made(tm) cap and a tweak to the base and collector bias works to some degree...sigh...
All those years on CB Tricks, and I have to start all over again...
Even AGC - simple yet needs to be "matched" by the radios' maker, so they can pinch off, cut down or even amplify - by affecting the Collector to Emitter voltages on the amplifier to affect their output.
Op amps, you have to get ones with null offset - and those are not popular as audio and RF don't mix well in these. You're better off just trimming bias to better match the coupling needed and stay with discrete.
Op Amps also have the inherent "Transistor to Transistor" intergration design which leaves you with no way of injecting a smoothing cap into any stage except to compensate or de-emphasis (as a whole - bootstrap or feedback from output to input) - and that takes a trick of two of knowing the construction of the inputs both inverting and non-inverting - to get that right.
Goldfinger offered several ways of modding radios - came from his own efforts. If and when you can, go back to the rec.radio.cb newsgroups days - you'll see a lot of criticisms over even making any changes to any portion of the audio path - lots to wade thru but what we tried to offer were other means to correct someone's else's desire to "remove a limiter", Cut out TRxx - snip this lead at Qxx Remove Rxxx kinda thing - before the Elhers law about the FCC no longer was required to exercise authority over interference disputes involving Citizens Band - now they are being treated as harassment claims and interference complaints on a local level as local enforcement concerns.
There's a lot to be said about speech processing...
:+> Andy <+:
I hear you really I do. I used tattoo money to buy a new scope and other gear. I wanted a scope and new gear more than I wanted a tattoo. LOL Sometimes you just need a tool and nothing else will do.
I love the feeling of independence that comes from learning new skills and doing what I can myself. Sometimes it is about money but not most of the time.I think men should be master's of their world and that comes from learning, understanding and doing! It is not enough to be book smart alone. If you never give up and you keep learning and doing over your lifetime it is good for us all! I think it is always good to know when you should pay an expert. LOL Sometimes you just do not have the time to learn a skill and get decent at it fast enough. What gets most people in trouble is they hit a snag and instead of backing up or stopping before they do more harm then good they forge ahead! LOL....I am sure we have all done this before at least once! LOL
Ok, I have been doing as much research on this speech processor as I possibly can. So far, the general consensus is that it is a benefit on SSB. My question is will this tax the finals more than say doing the NPC/RC mod & volting the final?
Any info would be greatly appreciated. I will probably go ahead & pick up one of these SP-1A anyways, I'd just like to know If I should keep an eye on the final.
Thank you for your time & knowledge.
It does raise the average modulation level by suppressing peaks. That alone makes a power stage work harder on sideband.
How much harder is up the the operator.